Articulating diamond-surfaced spinal implants

ABSTRACT

Articulating diamond-surfaced spinal implants are disclosed. Materials which may be used to make the spinal implants and manufacturing and finishing techniques for making the implants are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 09/494,240 filed on Jan. 30, 2000, now U.S. PatentNo. Priority is also claimed to U.S. Provisional Patent ApplicationSerial No. 60/315,545 filed on Aug. 28, 2001 and U.S. Provisional PatentApplication Serial No. 60/325,601 filed on Sep. 27, 2001.

BACKGROUND

[0002] In the past, various spinal implants were known. Most prior artspinal implants were adapted for fusion therapy, although there weresome articulating spinal implants as well.

SUMMARY

[0003] Various articulating diamond-surfaced spinal implants, materialsfor making them, and methods for making them.

BRIEF DESCRIPTION OF DRAWINGS

[0004] FIGS. 1A-1BB depict sintering of a polycrystalline diamondcompact.

[0005]FIGS. 1C & 1D depict formation of a diamond table on a substrateby a CVD, PVD or laser deposition method.

[0006] FIGS. 3-12 depict preparation of superhard materials for use inmaking an articulating diamond-surfaced spinal implant component.

[0007] FIGS. 13-36 depict final preparation of superhard materials priorto sintering.

[0008]FIG. 37 depicts the anvils of a cubic press that may be used inmaking superhard articulating diamond-surfaced spinal implantcomponents.

[0009] FIGS. 38-50 depict machining and finishing superhard articulatingdiamond-surfaced spinal implant components.

[0010]FIGS. 51 and 52 depict a human spine.

[0011] FIGS. 53 to 112-3 depict various embodiments of spinal implants.

DETAILED DESCRIPTION

[0012] Various embodiments of the devices disclosed herein relate tosuperhard surfaces for articulating diamond-surfaced spinal implants andmaterials of various compositions, devices of various geometries,attachment mechanisms, methods for making those superhard surfaces forarticulating diamond-surfaced spinal implants and components, andproducts, which include those superhard surfaces for articulatingdiamond-surfaced spinal implants and components. More specifically, someembodiments of the devices relate to diamond and sinteredpolycrystalline diamond surfaces and articulating diamond-surfacedspinal implants that include diamond and polycrystalline diamondsurfaces. Some embodiments of the devices utilize a polycrystallinediamond compact (“PDC”) to provide a very strong, low friction,long-wearing surface in an articulating diamond-surfaced spinal implant.Any surface, including surfaces outside the field of articulatingdiamond-surfaced spinal implants, which experience wear and requirestrength and durability will benefit from advances made here.

[0013] There are several design objectives for articulating spinalimplants. The implant should maintain height between adjacent vertebrae.It should produce translational stability of the vertebrae. It shouldprovide for intervertebral mobility. And the implant should reproducedisc kinematics. Some emobodiments of the spinal implants herein utilizecompound bearings and some use non-congruent bearings. One or more ofthe load bearing and articulation surfaces or contact surfaces of theimplant may utilize diamond for smooth and low-friction articulation.

[0014] The table below provides a comparison of sintered polycrystallinediamond (“PCD”) to some other materials. TABLE I COMPARISON OF SINTEREDPCD TO OTHER MATERIALS Thermal Hardness Conductivity CTE MaterialSpecific Gravity (Knoop) (W/m K) (×10⁻⁶) Sintered 3.5-4.0 9000 9001.50-4.8 Polycrystalline Diamond Compact Cubic Boron 3.48 4500 8001.0-4.0 Nitride Silicon Carbide 3.00 2500 84 4.7-5.3 Aluminum 3.50 20007.8-8.8 Oxide Tungsten 14.6 2200 112 4-6 Carbide (10% Co Cobalt Chrome8.2 43 RC 16.9 Ti6AI4V 4.43 6.6-17.5 11 Silicon Nitride 3.2 14.2 15-71.8-3.7

[0015] In view of the superior hardness of sintered PCD, it is expectedthat sintered PCD will provide improved wear and durabilitycharacteristics.

[0016] Reference will now be made to the drawings in which the variouselements of the present devices will be discussed. Persons skilled inthe design of articulating diamond-surfaced spinal implants and othersurfaces will understand the application of the various embodiments ofthe devices and their principles to articulating diamond-surfaced spinalimplants of all types, and components of articulating diamond-surfacedspinal implants, and devices other than those exemplified herein.

[0017] As discussed in greater detail below, the articulatingdiamond-surfaced spinal implant or articulating diamond-surfaced spinalimplant component may use polycrystalline diamond compacts in order toform durable load bearing and articulation surfaces. In apolycrystalline diamond compact that includes a substrate, the diamondtable may be chemically bonded and/or mechanically fixed to thesubstrate in a manufacturing process that may use a combination of highpressure and high temperature to form the sintered polycrystallinediamond. Alternatively, free-standing sintered polycrystalline diamondabsent a substrate may be formed. Free-standing diamond (without asubstrate) may also be referred to as solid diamond. The chemical bondsbetween diamond and a solvent-catalyst metal are established during thesintering process y combinations of unsatisfied sp3 carbon bonds withunsatisfied substrate metal bonds. Where a substrate is used, themechanical bond strength of the diamond table to the substrate thatresults is a consequence of shape of the substrate and diamond table anddifferences in the physical properties of the substrate and the diamondtable as well as the gradient interface between the substrate and thediamond table. The resulting sintered polycrystalline diamond compactforms a durable articulating diamond-surfaced spinal implant orcomponent.

[0018] The diamond table may be polished to a very smooth and glass-likefinish to achieve a very low coefficient of friction. The high surfaceenergy of sinterered polycrystalline diamond compact causes it to workvery well as a load-bearing and articulation surface when a lubricatingfluid is present. Its inherent nature allows it to perform very wellwhen a lubricant is absent as well.

[0019] While there is discussion herein concerning polycrystallinediamond compacts, the following materials could be considered forforming an articulating spinal implant or component: polycrystallinediamond, monocrystal diamond, natural diamond, diamond created byphysical vapor deposition, diamond created by chemical vapor deposition,diamond like carbon, carbonado, cubic boron nitride, hexagonal boronnitride, or a combination of these, cobalt, chromium, titanium,vanadium, stainless steel, niobium, aluminum, nickel, hafnium, silicon,tungsten, molybdenum, aluminum, zirconium, nitinol, cobalt chrome,cobalt chrome molybdenum, cobalt chrome tungsten, tungsten carbide,titanium carbide, tantalum carbide, zirconium carbide, hafnium carbide,Ti6/4, silicon carbide, chrome carbide, vanadium carbide, yttriastabilized zirconia, magnesia stabilized zirconia, zirconia toughenedalumina, titanium molybdenum hafnium, alloys including one or more ofthe above metals, ceramics, quartz, garnet, sapphire, combinations ofthese materials, combinations of these and other materials, and othermaterials may also be used for a desired articulating diamond-surfacedspinal implant or component.

[0020] Sintered Polycrystalline Diamond Compacts

[0021] One useful material for manufacturing articulatingdiamond-surfaced spinal implant surfaces, however, is a sinteredpolycrystalline diamond compact due to its superior performance. Diamondhas the greatest hardness and the lowest coefficient of friction of anycurrently known material. Sintered polycrystalline diamond compacts arechemically inert, are impervious to all solvents, and have the highestthermal conductivity at room temperature of any known material.

[0022] In some embodiments of the devices, a polycrystalline diamondcompact provides unique chemical bonding and mechanical grip between thediamond and the substrate material.

[0023] A method by which PDC may be manufactured is described later inthis document. Briefly, it involves sintering diamond crystals to eachother, and to a substrate under high pressure and high temperature.FIGS. 1A and 1B illustrate the physical and chemical processes involvedmanufacturing polycrystalline diamond compacts.

[0024] In FIG. 1A, a quantity of diamond feedstock 130 (such as diamondpowder or crystals) is placed adjacent to a metal-containing substrate110 prior to sintering. In the region of the diamond feedstock 130,individual diamond crystals 131 may be seen, and between the individualdiamond crystals 131 there are interstitial spaces 132. If desired, aquantity of solvent-catalyst metal may be placed into the interstitialspaces 132. The substrate may also contain solvent-catalyst metal.

[0025] The substrate 110 may be a suitable pure metal or alloy, or acemented carbide containing a suitable metal or alloy as a cementingagent such as cobalt-cemented tungsten carbide. The substrate may be ametal with high tensile strength. In a cobalt-chrome substrate of thedevices, the cobalt-chrome alloy will serve as a solvent-catalyst metalfor solvating diamond crystals during the sintering process.

[0026] The illustration shows the individual diamond crystals and thecontiguous metal crystals in the metal substrate. The interface 120between diamond powder and substrate material is a critical region wherebonding of the diamond table to the substrate must occur. In someembodiments of the devices, a boundary layer of a third materialdifferent than the diamond and the substrate is placed at the interface120. This interface boundary layer material, when present, may serveseveral functions including, but not limited to, enhancing the bond ofthe diamond table to the substrate, and mitigation of the residualstress field at the diamond-substrate interface.

[0027] Once diamond powder or crystals and substrate are assembled asshown in FIG. 1A, the assembly is subjected to high pressure and hightemperature as described later herein in order to cause bonding ofdiamond crystals to diamond crystals and to the substrate. The resultingstructure of sintered polycrystalline diamond table bonded to asubstrate is called a polycrystalline diamond compact (PDC). A compact,as the term is used herein, is a composite structure of two differentmaterials, such as diamond crystals, and a substrate metal. Theanalogous structure incorporating cubic boron nitride crystals in thesintering process instead of diamond crystals is called polycrystallinecubic boron nitride compact (PCBNC). Many of the processes describedherein for the fabrication and finishing of PDC structures and partswork in a similar fashion for PCBNC. In some embodiments of the devices,PCBNC may be substituted for PDC.

[0028]FIG. 1B depicts a polycrystalline diamond compact 101 after thehigh pressure and high temperature sintering of diamond feedstock to asubstrate. Within the PDC structure, there is an identifiable volume ofsubstrate 102, an identifiable volume of diamond table 103, and atransition zone 104 between diamond table and substrate containingdiamond crystals and substrate material. Crystalline grains of substratematerial 105 and sintered crystals of diamond 106 are depicted.

[0029] On casual examination, the finished compact of FIG. 1B willappear to consist of a solid table of diamond 103 attached to thesubstrate 402 with a discrete boundary. On very close examination,however, a transition zone 104 between diamond table 103 and substrate102 can be characterized. This zone represents a gradient interfacebetween diamond table and substrate with a gradual transition of ratiosbetween diamond content and metal content. At the substrate side of thetransition zone, there will be only a small percentage of diamondcrystals and a high percentage of substrate metal, and on the diamondtable side, there will be a high percentage of diamond crystals and alow percentage of substrate metal. Because of this gradual transition ofratios of polycrystalline diamond to substrate metal in the transitionzone, the diamond table and the substrate have a gradient interface.

[0030] In the transition zone or gradient transition zone where diamondcrystals and substrate metal are intermingled, chemical bonds are formedbetween the diamond and metal. From the transition zone 104 into thediamond table 103, the metal content diminishes and is limited tosolvent-catalyst metal that fills the three-dimensional vein-likestructure of interstitial voids, openings or asperities 107 within thesintered diamond table structure 103. The solvent-catalyst metal foundin the voids or openings 107 may have been swept up from the substrateduring sintering or may have been solvent-catalyst metal added to thediamond feedstock before sintering.

[0031] During the sintering process, there are three types of chemicalbonds that are created: diamond-to-diamond bonds, diamond-to-metalbonds, and metal-to-metal bonds. In the diamond table, there arediamond-to-diamond bonds (sp3 carbon bonds) created when diamondparticles partially solvate in the solvate-catalyst metal and then arebonded together. In the substrate and in the diamond table, there aremetal-to-metal bonds created by the high pressure and high temperaturesintering process. And in the gradient transition zone, diamond-to-metalbonds are created between diamond and solvent-catalyst metal.

[0032] The combination of these various chemical bonds and themechanical grip exerted by solvent-catalyst metal in the diamond tablesuch as in the interstitial spaces of the diamond structure diamondtable provide extraordinarily high bond strength between the diamondtable and the substrate. Interstitial spaces are present in the diamondstructure and those spaces typically are filled with solvent-catalystmetal, forming veins of solvent-catalyst metal within thepolycrystalline diamond structure. This bonding structure contributes tothe extraordinary fracture toughness of the compact, and the veins ofmetal within the diamond table act as energy sinks halting propagationof incipient cracks within the diamond structure. The transition zoneand metal vein structure provide the compact with a gradient of materialproperties between those of the diamond table and those of substratematerial, further contributing to the extreme toughness of the compact.The transition zone can also be called an interface, a gradienttransition zone, a composition gradient zone, or a composition gradient,depending on its characteristics. The transition zone distributesdiamond/substrate stress over the thickness of the zone, reducing zonehigh stress of a distinct linear interface. The subject residual stressis created as pressure and temperature are reduced at the conclusion ofthe high pressure/high temperature sintering process due to thedifference in pressure and thermal expansive properties of the diamondand substrate materials.

[0033] The diamond sintering process occurs under conditions ofextremely high pressure and high temperature. According to theinventors' best experimental and theoretical understanding, the diamondsintering process progresses through the following sequence of events.At pressure, a cell containing feedstock of unbonded diamond powder orcrystals (diamond feedstock) and a substrate is heated to a temperatureabove the melting point of the substrate metal 110 and molten metalflows or sweeps into the interstitial voids 107 between the adjacentdiamond crystals 106. It is carried by the pressure gradient to fill thevoids as well as being pulled in by the surface energy or capillaryaction of the large surface area of the diamond crystals 106. As thetemperature continues to rise, carbon atoms from the surface of diamondcrystals dissolve into this interstitial molten metal, forming a carbonsolution.

[0034] At the proper threshold of temperature and pressure, diamondbecomes the thermodynamically favored crystalline allotrope of carbon.As the solution becomes super saturated with respect to Cd (carbondiamond), carbon from this solution begins to crystallize as diamondonto the surfaces of diamond crystals bonding adjacent diamond crystalstogether with diamond-diamond bonds into a sintered polycrystallinediamond structure 106. The interstitial metal fills the remaining voidspace forming the vein-like lattice structure 107 within the diamondtable by capillary forces and pressure driving forces. Because of thecrucial role that the interstitial metal plays in forming a solution ofcarbon atoms and stabilizing these reactive atoms during the diamondcrystallization phase in which the polycrystalline diamond structure isformed, the metal is referred to as a solvent-catalyst metal.

[0035]FIG. 1 BB depicts a sintered polycrystalline diamond compacthaving both substrate metal 180 and diamond 181, but in which there is acontinuous gradient transition 182 from substrate metal to diamond. Insuch a compact, the gradient transition zone may be the entire compact,or a portion of the compact. The substrate side of the compact maycontain nearly pure metal for easy machining and attachment to othercomponents, while the diamond side may be extremely hard, smooth anddurable for use in a hostile work environment.

[0036] In some embodiments of the devices, a quantity ofsolvent-catalyst metal may be combined with the diamond feedstock priorto sintering. This is found to be useful when forming thick PCD tables,solid PDC structures, or when using multimodal fine diamond where thereis little residual free space within the diamond powder. In each ofthese cases, there may not be sufficient ingress of solvent-catalystmetal via the sweep mechanism to adequately mediate the sinteringprocess as a solvent-catalyst. The metal may be added by direct additionof powder, or by generation of metal powder in situ with an attritormill or by the well-known method of chemical reduction of metal saltsdeposited on diamond crystals. Added metal may constitute any amountfrom less than 1% by mass, to greater than 35%. This added metal mayconsist of the same metal or alloy as is found in the substrate, or maybe a different metal or alloy selected because of its material andmechanical properties. Example ratios of diamond feedstock tosolvent-catalyst metal prior to sintering include mass ratios of 70:30,85:15, 90:10, and 95:15. The metal in the diamond feedstock may be addedpowder metal, metal added by an attritor method, vapor deposition orchemical reduction of metal into powder.

[0037] When sintering diamond on a substrate with an interface boundarylayer, it may be that no solvent-catalyst metal from the substrate isavailable to sweep into the diamond table and participate in thesintering process. In this case, the boundary layer material, ifcomposed of a suitable material, metal or alloy that can function as asolvent-catalyst, may serve as the sweep material mediating the diamondsintering process. In other cases where the desired boundary materialcannot serve as a solvent-catalyst, a suitable amount ofsolvent-catalyst metal powder as described herein is added to thediamond crystal feed stock as described above. This assembly is thentaken through the sintering process. In the absence of a substrate metalsource, the solvent-catalyst metal for the diamond sintering processmust be supplied entirely from the added metal powder. The boundarymaterial may bond chemically to the substrate material, and bondschemically to the diamond table and/or the added solvent-catalyst metalin the diamond table. The remainder of the sintering and fabricationprocess may be the same as with the conventional solvent-catalyst sweepsintering and fabrication process.

[0038] For the sake of simplicity and clarity in this patent, thesubstrate, transition zone, and diamond table have been discussed asdistinct layers. However, it is important to realize that the finishedsintered object may be a composite structure characterized by acontinuous gradient transition from substrate material to diamond tablerather than as distinct layers with clear and discrete boundaries, hencethe term “compact”.

[0039] In addition to the sintering processes described above, diamondparts suitable for use as articulating diamond-surfaced spinal implantscomponents may also be fabricated as solid or free-standingpolycrystalline diamond structures without a substrate. These may beformed by placing the diamond powder combined with a suitable amount ofadded solvent-catalyst metal powder as described above in a refractorymetal can (typically Ta, Nb, Zr, or Mo) with a shape approximating theshape of the final part desired. This assembly is then taken through thesintering process. However, in the absence of a substrate metal source,the solvent-catalyst metal for the diamond sintering process must besupplied entirely from the added metal powder. With suitable finishing,objects thus formed may be used as is, or bonded to metal or othersubstrates.

[0040] Sintering is a method of creating a diamond table with a strongand durable constitution. Other methods of producing a diamond tablethat may or may not be bonded to a substrate are possible. At present,these typically are not as strong or durable as those fabricated withthe sintering process. It is also possible to use these methods to formdiamond structures directly onto substrates suitable for use asarticulating diamond-surfaced spinal implants. A table ofpolycrystalline diamond either with or without a substrate may bemanufactured and later attached to an articulating diamond-surfacedspinal implant in a location such that it will form a surface. Theattachment could be performed with any suitable method, includingwelding, brazing, sintering, diffusion welding, diffusion bonding,inertial welding, adhesive bonding, or the use of fasteners such asscrews, bolts, or rivets. In the case of attaching a diamond tablewithout a substrate to another object, the use of such methods asbrazing, diffusion welding/bonding or inertia welding may be mostappropriate.

[0041] Although high pressure/high temperature sintering is a method forcreating a diamond surface, other methods for producing a volume ofdiamond may be employed as well. For example, either chemical vapordeposition (CVD), or physical vapor deposition (PVD) processes may beused. CVD produces a diamond layer by thermally cracking an organicmolecule and depositing carbon radicals on a substrate. PVD produces adiamond layer by electrically causing carbon radicals to be ejected froma source material and to deposit on a substrate where they build adiamond crystal structure.

[0042] The CVD and PVD processes have some advantages over sintering.Sintering is performed in large, expensive presses at high pressure(such as 45-68 kilobars) and at high temperatures (such as 1200 to 1500degrees Celsius). It is difficult to achieve and maintain desiredcomponent shape using a sintering process because of flow of highpressure mediums used and possible deformation of substrate materials.

[0043] In contrast, CVD and PVD take place at atmospheric pressure orlower, so there no need for a pressure medium and there is nodeformation of substrates.

[0044] Another disadvantage of sintering is that it is difficult toachieve some geometries in a sintered polycrystalline diamond compact.When CVD or PVD are used, however, the gas phase used for carbon radicaldeposition can completely conform to the shape of the object beingcoated, making it easy to achieve a desired non-planar shape.

[0045] Another potential disadvantage of sintering polycrystallinediamond compacts is that the finished component will tend to have largeresidual stresses caused by differences in the coefficient of thermalexpansion and modulus between the diamond and the substrate. Whileresidual stresses can be used to improve strength of a part, they canalso be disadvantageous. When CVD or PVD is used, residual stresses canbe minimized because CVD and PVD processes do not involve a significantpressure transition (such from 68 Kbar to atmospheric pressure in highpressure and high temperature sintering) during manufacturing.

[0046] Another potential disadvantage of sintering polycrystallinediamond compacts is that few substrates have been found that aresuitable for sintering. Tungsten carbide is a common choice forsubstrate materials. When CVD or PVD are used, however, syntheticdiamond can be placed on many substrates, including titanium, mostcarbides, silicon, molybdenum and others. This is because thetemperature and pressure of the CVD and PVD coating processes are lowenough that differences in coefficient of thermal expansion and modulusbetween diamond and the substrate are not as critical as they are in ahigh temperature and high pressure sintering process.

[0047] A further difficulty in manufacturing sintered polycrystallinediamond compacts is that as the size of the part to be manufacturedincreases, the size of the press must increase as well. Sintering ofdiamond will only take place at certain pressures and temperatures, suchas those described herein. In order to manufacture larger sinteredpolycrystalline diamond compacts, ram pressure of the press (tonnage)and size of tooling (such as dies and anvils) must be increased in orderto achieve the necessary pressure for sintering to take place. Butincreasing the size and capacity of a press is more difficult thansimply increasing the dimensions of its components. There may be apractical physical size constraints on press size due to themanufacturing process used to produce press tooling.

[0048] Tooling for a press is typically made from cemented tungstencarbide. In order to make tooling, the cemented tungsten carbide issintered in a vacuum furnace followed by pressing in a hot isosaticpress (“HIP”) apparatus. Hipping must be performed in a manner thatmaintains uniform temperature throughout the tungsten carbide in orderto achieve uniform physical qualities and quality. These requirementsimpose a practical limit on the size tooling that can be produced for apress that is useful for sintering polycrystalline diamond compacts. Thelimit on the size tooling that can be produced also limits the sizepress that can be produced.

[0049] CVD and PVD manufacturing apparatuses may be scaled up in sizewith few limitations, allowing them to produce polycrystalline diamondcompacts of almost any desired size.

[0050] CVD and PVD processes are also advantageous because they permitprecise control of the thickness and uniformity of the diamond coatingto be applied to a substrate. Temperature is adjusted within the rangeof 500 to 1000 degrees Celsius, and pressure is adjusted in a range ofless than 1 atmosphere to achieve desired diamond coating thickness.

[0051] Another advantage of CVD and PVD processes is that they allow themanufacturing process to be monitored as it progresses. A CVD or PVDreactor can be opened before manufacture of a part is completed so thatthe thickness and quality of the diamond coating being applied to thepart may be determined. From the thickness of the diamond coating thathas already been applied, time to completion of manufacture can becalculated. Alternatively, if the coating is not of desired quality, themanufacturing processes may be aborted in order to save time and money.

[0052] In contrast, sintering of polycrystalline diamond compacts isperformed as a batch process that cannot be interrupted, and progress ofsintering cannot be monitored. The pressing process must be run tocompletion and the part may only be examined afterward.

[0053] CVD and PVD Diamond

[0054] CVD is performed in an apparatus called a reactor. A basic CVDreactor includes four components. The first component of the reactor isone or more gas inlets. Gas inlets may be chosen based on whether gasesare premixed before introduction to the chamber or whether the gases areallowed to mix for the first time in the chamber. The second componentof the reactor is one or more power sources for the generation ofthermal energy. A power source is needed to heat the gases in thechamber. A second power source may be used to heat the substratematerial uniformly in order to achieve a uniform coating of diamond onthe substrate. The third component of the reactor is a stage or platformon which a substrate is placed. The substrate will be coated withdiamond during the CVD process. Stages used include a fixed stage, atranslating stage, a rotating stage and a vibratory stage. Anappropriate stage must be chosen to achieved desired diamond coatingquality and uniformity. The fourth component of the reactor is an exitport for removing exhaust gas from the chamber. After gas has reactedwith the substrate, it must be removed from the chamber as quickly aspossible so that it does not participate in other reactions, which wouldbe deleterious to the diamond coating.

[0055] CVD reactors are classified according to the power source used.The power source is chosen to create the desired species necessary tocarry out diamond thin film deposition. Some CVD reactor types includeplasma-assisted microwave, hot filament, electron beam, single, doubleor multiple laser beam, arc jet and DC discharge. These reactors differin the way they impart thermal energy to the gas species and in theirefficiency in breaking gases down to the species necessary fordeposition of diamond. It is possible to have an array of lasers toperform local heating inside a high pressure cell. Alternatively, anarray of optical fibers could be used to deliver light into the cell.

[0056] The basic process by which CVD reactors work is as follows. Asubstrate is placed into the reactor chamber. Reactants are introducedto the chamber via one or more gas inlets. For diamond CVD, methane(CH₄) and hydrogen (H₂) gases may be brought into the chamber inpremixed form. Instead of methane, any carbon-bearing gas in which thecarbon has sp3 bonding may be used. Other gases may be added to the gasstream in order to control quality of the diamond film, depositiontemperature, gain structure and growth rate. These include oxygen,carbon dioxide, argon, halogens and others.

[0057] The gas pressure in the chamber may be maintained at about 100torr. Flow rates for the gases through the chamber may be about 10standard cubic centimeters per minute for methane and about 100 standardcubic centimeters per minute for hydrogen. The composition of the gasphase in the chamber may be in the range of 90-99.5% hydrogen and0.5-10% methane.

[0058] When the gases are introduced into the chamber, they are heated.Heating may be accomplished by many methods. In a plasma-assistedprocess, the gases are heated by passing them through a plasma.Otherwise, the gases may be passed over a series of wires such as thosefound in a hot filament reactor.

[0059] Heating the methane and hydrogen will break them down intovarious free radicals. Through a complicated mixture of reactions,carbon is deposited on the substrate and joins with other carbon to formcrystalline diamond by sp3 bonding. The atomic hydrogen in the chamberreacts with and removes hydrogen atoms from methyl radicals attached tothe substrate surface in order to create molecular hydrogen, leaving aclear solid surface for further deposition of free radicals.

[0060] If the substrate surface promotes the formation of sp2 carbonbonds, or if the gas composition, flow rates, substrate temperature orother variables are incorrect, then graphite rather than diamond willgrow on the substrate.

[0061] There are many similarities between CVD reactors and processesand PVD reactors and processes. PVD reactors differ from CVD reactors inthe way that they generate the deposition species and in the physicalcharacteristics of the deposition species. In a PVD reactor, a plate ofsource material is used as a thermal source, rather than having aseparate thermal source as in CVD reactors. A PVD reactor generateselectrical bias across a plate of source material in order to generateand eject carbon radicals from the source material. The reactor bombardsthe source material with high energy ions. When the high energy ionscollide with source material, they cause ejection of the desired carbonradicals from the source material. The carbon radicals are ejectedradially from the source material into the chamber. The carbon radicalsthen deposit themselves onto whatever is in their path, including thestage, the reactor itself, and the substrate.

[0062] Referring to FIG. 1C, a substrate 140 of appropriate material isdepicted having a deposition face 141 on which diamond may be depositedby a CVD or PVD process. FIG. 1D depicts the substrate 140 and thedeposition face 141 on which a volume of diamond 142 has been depositedby CVD or PVD processes. A small transition zone 143 is present in whichboth diamond and substrate are located. In comparison to FIG. 1B, it canbe seen that the CVD or PVD diamond deposited on a substrate lacks themore extensive gradient transition zone of sintered polycrystallinediamond compacts because there is no sweep of solvent-catalyst metalthrough the diamond table in a CVD or PVD process.

[0063] Both CVD and PVD processes achieve diamond deposition by line ofsight. Means (such as vibration and rotation) are provided for exposingall desired surfaces for diamond deposition. If a vibratory stage is tobe used, the surface will vibrate up and down with the stage and therebypresent all surfaces to the free radical source.

[0064] There are several methods, which may be implemented in order tocoat cylindrical objects with diamond using CVD or PVD processes. If aplasma assisted microwave process is to be used to achieve diamonddeposition, then the object to receive the diamond must be directlyunder the plasma in order to achieve the highest quality and mostuniform coating of diamond. A rotating or translational stage may beused to present every aspect of the surface to the plasma for diamondcoating. As the stage rotates or translates, all portions of the surfacemay be brought directly under the plasma for coating in such a way toachieve sufficiently uniform coating.

[0065] If a hot filament CVD process is used, then the surface should beplaced on a stationary stage. Wires or filaments (typically tungsten)are strung over the stage so that their coverage includes the surface tobe coated. The distance between the filaments and the surface and thedistance between the filaments themselves may be chosen to achieve auniform coating of diamond directly under the filaments.

[0066] Diamond surfaces can be manufactured by CVD and PVD processeither by coating a substrate with diamond or by creating a freestanding volume of diamond, which is later mounted for use. A freestanding volume of diamond may be created by CVD and PVD processes in atwo-step operation. First, a thick film of diamond is deposited on asuitable substrate, such as silicon, molybdenum, tungsten or others.Second, the diamond film is released from the substrate.

[0067] As desired, segments of diamond film may be cut away, such as byuse of a Q-switched YAG laser. Although diamond is transparent to a YAGlaser, there is usually a sufficient amount of sp2 bonded carbon (asfound in graphite) to allow cutting to take place. If not, then a linemay be drawn on the diamond film using a carbon-based ink. The lineshould be sufficient to permit cutting to start, and once started,cutting will proceed slowly.

[0068] After an appropriately-sized piece of diamond has been cut from adiamond film, it can be attached to a desired object in order to serveas a surface. For example, the diamond may be attached to a substrate bywelding, diffusion bonding, adhesion bonding, mechanical fixation orhigh pressure and high temperature bonding in a press.

[0069] Although CVD and PVD diamond on a substrate do not exhibit agradient transition zone that is found in sintered polycrystallinediamond compacts, CVD and PVD process can be conducted in order toincorporate metal into the diamond table. As mentioned elsewhere herein,incorporation of metal into the diamond table enhances adhesion of thediamond table to its substrate and can strengthen the polycrystallinediamond compact. Incorporation of diamond into the diamond table can beused to achieve a diamond table with a coefficient of thermal expansionand compressibility different from that of pure diamond, andconsequently increasing fracture toughness of the diamond table ascompared to pure diamond. Diamond has a low coefficient of thermalexpansion and a low compressibility compared to metals. Therefore thepresence of metal with diamond in the diamond table achieves a higherand more metal-like coefficient of thermal expansion and the averagecompressibility for the diamond table than for pure diamond.Consequently, residual stresses at the interface of the diamond tableand the substrate are reduced, and delamination of the diamond tablefrom the substrate is less likely.

[0070] A pure diamond crystal also has low fracture toughness.Therefore, in pure diamond, when a small crack is formed, the entirediamond component fails catastrophically. In comparison, metals have ahigh fracture toughness and can accommodate large cracks withoutcatastrophic failure. Incorporation of metal into the diamond tableachieves a greater fracture toughness than pure diamond. In a diamondtable having interstitial spaces and metal within those interstitialspaces, if a crack forms in the diamond and propagates to aninterstitial space containing metal, the crack will terminate at themetal and catastrophic failure will be avoided. Because of thischaracteristic, a diamond table with metal in its interstitial spaces isable to sustain much higher forces and workloads without catastrophicfailure compared to pure diamond.

[0071] Diamond-diamond bonding tends to decrease as metal content in thediamond table increases. CVD and PVD processes can be conducted so thata transition zone is established. However, the surface can beessentially pure polycrystalline diamond for low wear properties.

[0072] Generally CVD and PVD diamond is formed without largeinterstitial spaces filled with metal. Consequently, most PVD and CVDdiamond is more brittle or has a lower fracture toughness than sinteredpolycrystalline diamond compacts. CVD and PVD diamond may also exhibitthe maximum residual stresses possible between the diamond table and thesubstrate. It is possible, however, to form CVD and PVD diamond filmthat has metal incorporated into it with either a uniform or afunctionally gradient composition.

[0073] One method for incorporating metal into a CVD or PVD diamond filmit to use two different source materials in order to simultaneouslydeposit the two materials on a substrate in a CVD of PVD diamondproduction process. This method may be used regardless of whetherdiamond is being produced by CVD, PVD or a combination of the two.

[0074] Another method for incorporating metal into a CVD diamond filmchemical vapor infiltration. This process would first create a porouslayer of material, and then fill the pores by chemical vaporinfiltration. The porous layer thickness should be approximately equalto the desired thickness for either the uniform or gradient layer. Thesize and distribution of the pores can be sued to control ultimatecomposition of the layer. Deposition in vapor infiltration occurs firstat the interface between the porous layer and the substrate. Asdeposition continues, the interface along which the material isdeposited moves outward from the substrate to fill pores in the porouslayer. As the growth interface moves outward, the deposition temperaturealong the interface is maintained by moving the sample relative to aheater or by moving the heater relative to the growth interface. It isimperative that the porous region between the outside of the sample andthe growth interface be maintained at a temperature that does notpromote deposition of material (either the pore-filling material orundesired reaction products). Deposition in this region would close thepores prematurely and prevent infiltration and deposition of the desiredmaterial in inner pores. The result would be a substrate with openporosity and poor physical properties.

[0075] Laser Deposition of Diamond

[0076] Another alternative manufacturing process that may be used toproduce surfaces and components of the devices involves use of energybeams, such as laser energy, to vaporize constituents in a substrate andredeposit those constituents on the substrate in a new form, such as inthe form of a diamond coating. As an example, a metal, polymeric orother substrate may be obtained or produced containing carbon, carbidesor other desired constituent elements. Appropriate energy, such as laserenergy, may be directed at the substrate to cause constituent elementsto move from within the substrate to the surface of the substrateadjacent the area of application of energy to the substrate. Continuedapplication of energy to the concentrated constituent elements on thesurface of the substrate can be used to cause vaporization of some ofthose constituent elements. The vaporized constituents may then bereacted with another element to change the properties and structure ofthe vaporized constituent elements.

[0077] Next, the vaporized and reacted constituent elements (which maybe diamond) may be diffused into the surface of the substrate. Aseparate fabricated coating may be produced on the surface of thesubstrate having the same or a different chemical composition than thatof the vaporized and reacted constituent elements. Alternatively, someof the changed constituent elements which were diffused into thesubstrate may be vaporized and reacted again and deposited as a coatingon the. By this process and variations of it, appropriate coatings suchas diamond, cubic boron nitride, diamond like carbon, B₄C, SiC, TiC,TiN, TiB, cCN, Cr₃C₂, and Si₃N₄ may be formed on a substrate.

[0078] In other manufacturing environments, high temperature laserapplication, electroplating, sputtering, energetic laser excited plasmadeposition or other methods may be used to place a volume of diamond,diamond-like material, a hard material or a superhard material in alocation in which will serve as a surface.

[0079] In light of the disclosure herein, those of ordinary skill in theart will comprehend the apparatuses, materials and process conditionsnecessary for the formation and use of high quality diamond on asubstrate using any of the manufacturing methods described herein inorder to create a diamond surface.

[0080] Material Property Considerations

[0081] There is a particular problem posed by the manufacture of anon-planar diamond surface. The non-planar component design requiresthat pressures be applied radially in making the part. During the highpressure sintering process, described in detail below, all displacementsmust be along a radian emanating from the center of the part that willbe produced in order to achieve the desired non-planar geometry. Toachieve this in high temperature/high pressure pressing, an isostaticpressure field must be created. During the manufacture of suchnon-planar parts, if there is any deviatoric stress component, it willresult in distortion of the part and may render the manufactured partuseless.

[0082] Special considerations that must be taken into account in makingnon-planar polycrystalline diamond compacts are discussed below.

[0083] Modulus

[0084] Most polycrystalline diamond compacts include both a diamondtable and a substrate. The material properties of the diamond and thesubstrate may be compatible, but the high pressure and high temperaturesintering process in the formation of a polycrystalline diamond compactmay result in a component with excessively high residual stresses. Forexample, for a polycrystalline diamond compact using tungsten carbide asthe substrate, the sintered diamond has a Young's modulus ofapproximately 120 million p.s.i., and cobalt cemented tungsten carbidehas a modulus of approximately 90 million p.s.i. Modulus refers to theslope of the curve of the stress plotted against the stress for amaterial. Modulus indicates the stiffness of the material. Bulk modulusrefers to the ratio of isostatic strain to isostatic stress, or the unitvolume reduction of a material versus the applied pressure or stress.

[0085] Because diamond and most substrate materials have such a highmodulus, a very small stress or displacement of the polycrystallinediamond compact can induce very large stresses. If the stresses exceedthe yield strength of either the diamond or the substrate, the componentwill fail. The strongest polycrystalline diamond compact is notnecessarily stress free. In a sintered polycrystalline diamond compactwith optimal distribution of residual stress, more energy is required toinduce a fracture than in a stress free component. Thus, the differencein modulus between the substrate and the diamond must be noted and usedto design a component that will have the best strength for itsapplication with sufficient abrasion resistance and fracture toughness.

[0086] Coefficient of Thermal Expansion (CTE)

[0087] The extent to which diamond and its substrate differ in how theydeform relative to changes in temperature also affects their mechanicalcompatibility. Coefficient of thermal expansion (“CTE”) is a measure ofthe unit change of a dimension with unit change in temperature or thepropensity of a material to expand under heat or to contract whencooled. As a material experiences a phase change, calculations based onCTE in the initial phase will not be applicable. It is notable that whencompacts of materials with different CTE's and moduluses are used, theywill stress differently at the same stress.

[0088] Polycrystalline diamond has a coefficient of thermal expansion(as above and hereafter referred to as “CTE” on the order of 2-4 microinches per inch (10⁻⁶ inches) of material per degree (in/in° C.). Incontrast, carbide has a CTE on the order of 6-8 in/in° C. Although thesevalues appear to be close numerically, the influence of the high moduluscreates very high residual stress fields when a temperature gradient ofa few hundred degrees is imposed upon the combination of substrate anddiamond. The difference in coefficient of thermal expansion is less of aproblem in simple planarl polycrystalline diamond compacts than in themanufacture of non-planar or complex shapes. When a non-planarpolycrystalline diamond compact is manufactured, differences in the CTEbetween the diamond and the substrate can cause high residual stresswith subsequent cracking and failure of the diamond table, the substrateor both at any time during or after high pressure/high temperaturesintering.

[0089] Dilatoric and Deviatoric Stresses

[0090] The diamond and substrate assembly will experience a reduction offree volume during the sintering process. The sintering process,described in detail below, involves subjecting the substrate and diamondassembly to pressure ordinarily in the range of about 40 to about 68kilobar. The pressure will cause volume reduction of the substrate. Somegeometrical distortion of the diamond and/or the substrate may alsooccur. The stress that causes geometrical distortion is calleddeviatoric stress, and the stress that causes a change in volume iscalled dilatoric stress. In an isostatic system, the deviatoric stressessum to zero and only the dilatoric stress component remains. Failure toconsider all of these stress factors in designing and sintering apolycrystalline diamond component with complex geometry (such as concaveand convex non-planar polycrystalline diamond compacts) will likelyresult in failure of the process.

[0091] Free Volume Reduction of Diamond Feedstock

[0092] As a consequence of the physical nature of the feedstock diamond,large amounts of free volume are present unless special preparation ofthe feedstock is undertaken prior to sintering. It is necessary toeliminate as much of the free volume in the diamond as possible, and ifthe free volume present in the diamond feedstock is too great, thensintering may not occur. It is also possible to eliminate the freevolume during sintering if a press with sufficient ram displacement isemployed. Is important to maintain a desired uniform geometry of thediamond and substrate during any process which reduces free volume inthe feedstock, or a distorted or faulty component may result.

[0093] Selection of Solvent-Catalyst Metal

[0094] Formation of synthetic diamond in a high temperature and highpressure press without the use of a solvent-catalyst metal is not aviable method at this time, although it may become viable in the future.A solvent-catalyst metal is at this time required to achieve desiredcrystal formation in synthetic diamond. The solvent-catalyst metal firstsolvates carbon preferentially from the sharp contact points of thediamond feedstock crystals. It then recrystallizes the carbon as diamondin the interstices of the diamond matrix with diamond-diamond bondingsufficient to achieve a solid with 95 to 97% of theoretical density withsolvent metal 5-3% by volume. That solid distributed over the substratesurface is referred to herein as a polycrystalline diamond table. Thesolvent-catalyst metal also enhances the formation of chemical bondswith substrate atoms.

[0095] A method for adding the solvent-catalyst metal to diamondfeedstock is by causing it to sweep from the substrate that containssolvent-catalyst metal during high pressure and high temperaturesintering. Powdered solvent-catalyst metal may also be added to thediamond feedstock before sintering, particularly if thicker diamondtables are desired. An attritor method may also be used to add thesolvent-catalyst metal to diamond feedstock before sintering. If toomuch or too little solvent-catalyst metal is used, then the resultingpart may lack the desired mechanical properties, so it is important toselect an amount of solvent-catalyst metal and a method for adding it todiamond feedstock that is appropriate for the particular part to bemanufactured.

[0096] Diamond Feedstock Particle Size and Distribution

[0097] The durability of the finished diamond product is integrallylinked to the size of the feedstock diamond and also to the particledistribution. Selection of the proper size(s) of diamond feedstock andparticle distribution depends upon the service requirement of thespecimen and also its working environment. The durability ofpolycrystalline diamond is enhanced if smaller diamond feedstockcrystals are used and a highly diamond-diamond bonded diamond table isachieved.

[0098] Although polycrystalline diamond may be made from single modaldiamond feedstock, use of multi-modal feedstock increases both impactstrength and wear resistance. The use of a combination of large crystalsizes and small crystal sizes of diamond feedstock together provides apart with high impact strength and wear resistance, in part because theinterstitial spaces between the large diamond crystals may be filledwith small diamond crystals. During sintering, the small crystals willsolvate and reprecipitate in a manner that binds all of the diamondcrystals into a strong and tightly bonded compact.

[0099] Diamond Feedstock Loading Methodology

[0100] Contamination of the diamond feedstock before or during loadingwill cause failure of the sintering process. Great care must be taken toensure the cleanliness of diamond feedstock and any addedsolvent-catalyst metal or binder before sintering.

[0101] In order to prepare for sintering, clean diamond feedstock,substrate, and container components are prepared for loading. Thediamond feedstock and the substrate are placed into a refractory metalcontainer called a “can” which will seal its contents from outsidecontamination. The diamond feedstock and the substrate will remain inthe can while undergoing high pressure and high temperature sintering inorder to form a polycrystalline diamond compact. The can may be sealedby electron beam welding at high temperature and in a vacuum.

[0102] Enough diamond aggregate (powder or grit) is loaded to accountfor linear shrinkage during high pressure and high temperaturesintering. The method used for loading diamond feedstock into a can forsintering affects the general shape and tolerances of the final part. Inparticular, the packing density of the feedstock diamond throughout thecan should be as uniform as possible in order to produce a good qualitysintered polycrystalline diamond compact structure. In loading, bridgingof diamond can be avoided by staged addition and packing.

[0103] The degree of uniformity in the density of the feedstock materialafter loading will affect geometry of the polycrystalline diamondcompact. Loading of the feedstock diamond in a dry form versus loadingdiamond combined with a binder and the subsequent process applied forthe removal of the binder will also affect the characteristics of thefinished polycrystalline diamond compact. In order to properlypre-compact diamond for sintering, the pre-compaction pressures shouldbe applied under isostatic conditions.

[0104] Selection of Substrate Material

[0105] The unique material properties of diamond and its relativedifferences in modulus and CTE compared to most potential substratematerials diamond make selection of an appropriate polycrystallinediamond substrate a formidable task. A great disparity in materialproperties between the diamond and the substrate creates challengessuccessful manufacture of a polycrystalline diamond component with theneeded strength and durability. Even very hard substrates appear to besoft compared to polycrystalline diamond. The substrate and the diamondmust be able to withstand not only the pressure and temperature ofsintering, but must be able to return to room temperature andatmospheric pressure without delaminating, cracking or otherwisefailing.

[0106] Selection of substrate material also requires consideration ofthe intended application for the part, impact resistance and strengthsrequired, and the amount of solvent-catalyst metal that will beincorporated into the diamond table during sintering. Substratematerials must be selected with material properties that are compatiblewith those of the diamond table to be formed.

[0107] Substrate Geometry

[0108] Further, it is important to consider whether to use a substratewhich has a smooth surface or a surface with topographical features.Substrate surfaces may be formed with a variety of topographicalfeatures so that the diamond table is fixed to the substrate with both achemical bond and a mechanical grip. Use of topographical features onthe substrate provides a greater surface area for chemical bonds andwith the mechanical grip provided by the topographical features, canresult in a stronger and more durable component.

[0109] Example Materials and Manufacturing Steps

[0110] The inventors have discovered and determined materials andmanufacturing processes for constructing polycrystalline diamondcompacts for use in an articulating diamond-surfaced spinal implant. Itis also possible to manufacture the invented surfaces by methods andusing materials other than those listed below.

[0111] The steps described below, such as selection of substratematerial and geometry, selection of diamond feedstock, loading andsintering methods, will affect each other, so although they are listedas separate steps that must be taken to manufacture a polycrystallinediamond compact, no step is completely independent of the others, andall steps must be standardized to ensure success of the manufacturingprocess.

[0112] Select Substrate and/or Solvent-Catalyst Metal

[0113] In order to manufacture any polycrystalline diamond component, anappropriate substrate should be selected. For the manufacture of apolycrystalline diamond component to be used in an articulatingdiamond-surfaced spinal implant, various substrates may be used asdesired. TABLE 2 SOME SUBSTRATES FOR ARTICULATING DIAMOND-SURFACEDSPINAL IMPLANT APPLICATIONS SUBSTRATE ALLOY NAME REMARKS TitaniumTi6/4(TiAIVa) A thin tantalum barrier may ASTM F-1313 (TiNbZr) be placedon the titanium ASTM F-620 substrate before loading ASTM F-1580 diamondfeedstock. TiMbHf Nitinol (TiNi + other) Cobalt chrome ASTM F-799Contains cobalt, chromium and molybdenum. Wrought product Cobalt chromeASTM F-90 Contains cobalt, chromium, tungsten and nickel. Cobalt chromeASTM F-75 Contains cobalt, chromium and molybdenum. Cast product. Cobaltchrome ASTM F-562 Contains cobalt, chromium, molybdenum and nickel.Cobalt chrome ASTM F-563 Contains cobalt, chromium, molybdenum,tungsten, iron and nickel. Tantalum ASTM F-560 (unalloyed) refractorymetal. Platinum various Niobium ASTM F-67 (unalloyed) refractory metal.Maganese Various May include Cr, Ni, Mg, molybdenum. Cobalt cemented WCCommonly used in tungsten carbide synthetic diamond production Cobaltchrome CoCr cemented WC cemented tungsten carbide Cobalt chrome CoCrcemented CrC cemented chrome carbide Cobalt chrome CoCr cemented SiCcemented silicon carbide Fused silicon SiC carbide Cobalt chrome CoCrMoA thin tungsten or molybdenum tungsten/cobalt layer may be placed on thesubstrate before loading diamond feedstock. Stainless steel Various

[0114] The CoCr used as a substrate or solvent-catalyst metal may beCoCrMo or CoCrW or another suitable CoCr. Alternatively, an Fe-basedalloy, a Ni-based alloy (such as Co—Cr—W—Ni) or another alloy may beused. Co and Ni alloys tend to provide a corrosion-resistant component.The preceding substrates and solvent-catalyst metals are examples only.In addition to these substrates, other materials may be appropriate foruse as substrates for construction of articulating diamond-surfacedspinal implant s and other surfaces.

[0115] When titanium is used as the substrate, sometimes place a thintantalum barrier layer is placed on the titanium substrate. The tantalumbarrier prevents mixing of the titanium alloys with cobalt alloys usedin the diamond feedstock. If the titanium alloys and the cobalt alloysmix, it possible that a detrimentally low melting point eutecticinter-metallic compound will be formed during the high pressure and hightemperature sintering process. The tantalum barrier bonds to both thetitanium and cobalt alloys, and to the polycrystalline diamond thatcontains cobalt solvent-catalyst metals. Thus, a polycrystalline diamondcompact made using a titanium substrate with a tantalum barrier layerand diamond feedstock that has cobalt solvent-catalyst metals can bevery strong and well formed. Alternatively, the titanium substrate maybe provided with an alpha case oxide coating (an oxidation layer)forming a barrier which prevents formation of a eutectic metal.

[0116] If a cobalt chrome molybdenum substrate is used, a thin tungstenlayer or a thin tungsten and cobalt layer can be placed on the substratebefore loading of the diamond feedstock in order to control formation ofchrome carbide (CrC) during sintering.

[0117] In addition to those listed, other appropriate substrates may beused for forming polycrystalline diamond compact surfaces. Further, itis possible within the scope of the devices to form a diamond surfacefor use without a substrate. It is also possible to form a surface fromany of the superhard materials and other materials listed herein, inwhich case a substrate may not be needed. Additionally, if it is desiredto use a type of diamond or carbon other than polycrystalline diamond,substrate selection may differ. For example, if a diamond surface is tobe created by use of chemical vapor deposition or physical vapordeposition, then use of a substrate appropriate for those manufacturingenvironments and for the compositions used will be necessary.

[0118] Determination of Substrate Geometry

[0119] A substrate geometry appropriate for the compact to bemanufactured and appropriate for the materials being used should beselected. In order to manufacture a non-planar diamond surface, it isnecessary to select a substrate geometry that will facilitate themanufacture of those parts. In order to ensure proper diamond formationand avoid compact distortion, forces acting on the diamond and thesubstrate during sintering must be strictly radial. Therefore thesubstrate geometry at the contact surface with diamond feedstock formanufacturing a complex surface in some instances may be generallynon-planar.

[0120] As mentioned previously, there is a great disparity in thematerial characteristics of synthetic diamond and most availablesubstrate materials. In particular, modulus and CTE are of concern. Butwhen applied in combination with each other, some substrates can form astable and strong polycrystalline diamond compact. The table below listsphysical properties of some substrate materials. TABLE 3 MATERIALPROPERTIES OF SOME EXAMPLE SUBSTRATES SUBSTRATE MATERIAL MODULUS CTE Ti6/4 16.5 million psi 5.4 CoCrMo 35.5 million psi 16.9 CoCrW 35.3 millionpsi 16.3

[0121] Use of either titanium or cobalt chrome substrates alone for themanufacture of non-planar polycrystalline diamond compacts may result incracking of the diamond table or separation of the substrate from thediamond table. In particular, it appears that titanium's dominantproperty during high pressure and high temperature sintering iscompressibility while cobalt chrome's dominant property during sinteringis CTE. In some embodiments of the devices, a substrate of two or morelayers may be used in order to achieve dimensional stability during andafter manufacturing.

[0122] In various embodiments of the devices, a single layer substratemay be utilized. In other embodiments of the devices, a two-layersubstrate may be utilized, as discussed. Depending on the properties ofthe components being used, however, it may be desired to utilize asubstrate that includes three, four or more layers. Such multi-layersubstrates are intended to be comprehended within the scope of thedevices.

[0123] Substrate Surface Topography

[0124] Depending on the application, it may be advantageous to includesubstrate surface topographical features on a substrate that is to beformed into a polycrystalline diamond compact. Regardless whether aone-piece, a two-piece of a multi-piece substrate is used, it may bedesirable to modify the surface of the substrate or providetopographical features on the substrate in order to increase the totalsurface area of diamond to enhance substrate to diamond contact and toprovide a mechanical grip of the diamond table.

[0125] The placement of topographical features on a substrate serves tomodify the substrate surface geometry or contours from what thesubstrate surface geometry or contours would be if formed as a simpleplanar or non-planar figure. Substrate surface topographical featuresmay include one or more different types of topographical features whichresult in protruding, indented or contoured features that serve toincrease surface, mechanically interlock the diamond table to thesubstrate, prevent crack formation, or prevent crack propagation.

[0126] Substrate surface topographical features or substrate surfacemodifications serve a variety of useful functions. Use of substratetopographical features increases total substrate surface area of contactbetween the substrate and the diamond table. This increased surface areaof contact between diamond table and substrate results in a greatertotal number of chemical bonds between diamond table and substrate thanif the substrate surface topographical features were absent, thusachieving a stronger polycrystalline diamond compact.

[0127] Substrate surface topographical features also serve to create amechanical interlock between the substrate and the diamond table. Themechanical interlock is achieved by the nature of the substratetopographical features and also enhances strength of the polycrystallinediamond compact.

[0128] Substrate surface topographical features may also be used todistribute the residual stress field of the polycrystalline diamondcompact over a larger surface area and over a larger volume of diamondand substrate material. This greater distribution can be used to keepstresses below the threshold for crack initiation and/or crackpropagation at the diamond table/substrate interface, within the diamonditself and within the substrate itself.

[0129] Substrate surface topographical features increase the depth ofthe gradient interface or transition zone between diamond table andsubstrate, in order to distribute the residual stress field through alonger segment of the composite compact structure and to achieve astronger part.

[0130] Substrate surface modifications can be used to created a sinteredpolycrystalline diamond compact that has residual stresses that fortifythe strength of the diamond layer and yield a more robustpolycrystalline diamond compact with greater resistance to breakage thanif no surface topographical features were used. This is because in orderto break the diamond layer, it is necessary to first overcome theresidual stresses in the part and then overcome the strength of thediamond table.

[0131] Substrate surface topographical features redistribute forcesreceived by the diamond table. Substrate surface topographical featurescause a force transmitted through the diamond layer to be re-transmittedfrom single force vector along multiple force vectors. Thisredistribution of forces travelling to the substrate avoids conditionsthat would deform the substrate material at a more rapid rate than thediamond table, as such differences in deformation can cause cracking andfailure of the diamond table.

[0132] Substrate surface topographical features may be used to mitigatethe intensity of the stress field between the diamond and the substratein order to achieve a stronger part.

[0133] Substrate surface topographical features may be used todistribute the residual stress field throughout the polycrystallinediamond compact structure in order to reduce the stress per unit volumeof structure.

[0134] Substrate surface topographical features may be used tomechanically interlock the diamond table to the substrate by causing thesubstrate to compress over an edge of the diamond table duringmanufacturing. Dovetailed, heminon-planar and lentate modifications actto provide force vectors that tend to compress and enhance the interfaceof diamond table and substrate during cooling as the substrate dilitatesradially.

[0135] Substrate surface topographical features may also be used toachieve a manufacturable form. As mentioned herein, differences incoefficient of thermal expansion and modulus between diamond and thechosen substrate may result in failure of the polycrystalline diamondcompact during manufacturing. For certain parts, the stronger interfacebetween substrate and diamond table that may be achieved when substratetopographical features are used can achieve a polycrystalline diamondcompact that can be successfully manufactured. But if a similar part ofthe same dimensions is to be made using a substrate with a simplesubstrate surface rather than specialized substrate surfacetopographical features, the diamond table may crack or separate from thesubstrate due to differences in coefficient of thermal expansion ormodulus of the diamond and the substrate.

[0136] Examples of useful substrate surface topographical featuresinclude waves, grooves, ridges, other longitudinal surface features (anyof which may be arranged longitudinally, lattitudinally, crossing eachother at a desired angle, in random patterns, and in geometricpatterns), three dimensional textures, non-planar segment depressions,non-planar segment protrusions, triangular depressions, triangularprotrusions, arcuate depressions, arcuate protrusions, partiallynon-planar depressions, partially non-planar protrusions, cylindricaldepressions, cylindrical protrusions, rectangular depressions,rectangular protrusions, depressions of n-sided polygonal shapes where nis an integer, protrusions of n-sided polygonal shapes, a waffle patternof ridges, a waffle iron pattern of protruding structures, dimples,nipples, protrusions, ribs, fenestrations, grooves, troughs or ridgesthat have a cross-sectional shape that is rounded, triangular, arcuate,square, polygonal, curved, or otherwise, or other shapes. Machining,pressing, extrusion, punching, injection molding and other manufacturingtechniques for creating such forms may be used to achieve desiredsubstrate topography. Although for illustration purposes, some sharpcorners are depicted on substrate topography or other structures in thedrawings, in practice it is expected that all corners will have a smallradius to achieve a component with superior durability.

[0137] Although many substrate topographies have been depicted in convexnon-planar substrates, those surface topographies may be applied toconvex non-planar substrate surfaces, other non-planar substratesurfaces, and flat substrate surfaces. Substrate surface topographieswhich are variations or modifications of those shown, and othersubstrate topographies which increase component strength or durabilitymay also be used.

[0138] Diamond Feedstock Selection

[0139] It is anticipated that typically the diamond particles used willbe in the range of less than 1 micron to more than 100 microns. In someembodiments of the devices, however, diamond particles as small as 1nanometer may be used. Smaller diamond particles are used for smoothersurfaces. Commonly, diamond particle sizes will be in the range of 0.5to 2.0 microns or 0.1 to 10 microns.

[0140] An example diamond feedstock is shown in the table below. TABLE 4EXAMPLE BIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT 4 to 8 micron diamondabout 90% 0.5 to 1.0 micron diamond about 9% Titanium carbonitridepowder about 1%

[0141] This formulation mixes some smaller and some larger diamondcrystals so that during sintering, the small crystals may dissolve andthen recrystallize in order to form a lattice structure with the largerdiamond crystals. Titanium carbonitride powder may optionally beincluded in the diamond feedstock in order to prevent excessive diamondgrain growth during sintering in order to produce a finished productthat has smaller diamond crystals.

[0142] Another diamond feedstock example is provided in the table below.TABLE 5 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size ×diamond crystals about 90% Size 0.1 × diamond crystals about 9% Size0.01 × diamond crystals about 1%

[0143] The trimodal diamond feedstock described above can be used withany suitable diamond feedstock having a first size or diameter “x”, asecond size 0.1x and a third size 0.01x. This ratio of diamond crystalsallows packing of the feedstock to about 89% theoretical density,closing most interstitial spaces and providing the densest diamond tablein the finished polycrystalline diamond compact.

[0144] Another diamond feedstock example is provided in the table below.TABLE 6 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size ×diamond crystals about 88-92% Size 0.1 × diamond crystals about 8-12%Size 0.01 × diamond crystals about 0.8-1.2%

[0145] Another diamond feedstock example is provided in the table below.TABLE 7 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size ×diamond crystals about 85-95% Size 0.1 × diamond crystals about 5-15%Size 0.01 × diamond crystals about 0.5-1.5%

[0146] Another diamond feedstock example is provided in the table below.TABLE 8 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size ×diamond crystals about 80-90% Size 0.1 × diamond crystals about 10-20%Size 0.01 × diamond crystals about 0-2%

[0147] In some embodiments of the devices, the diamond feedstock usedwill be diamond powder having a greatest dimension of about 100nanometers or less. In some embodiments of the devices somesolvent-catalyst metal is included with the diamond feedstock to aid inthe sintering process, although in many applications there will be asignificant solvent-catalyst metal sweep from the substrate duringsintering as well.

[0148] Solvent Metal Selection

[0149] It has already been mentioned that solvent metal will sweep fromthe substrate through the diamond feedstock during sintering in order tosolvate some diamond crystals so that they may later recrystallize andform a diamond-diamond bonded lattice network that characterizespolycrystalline diamond. It is possible to include some solvent-catalystmetal in the diamond feedstock only when required to supplement thesweep of solvent-catalyst metal from the substrate.

[0150] Traditionally, cobalt, nickel and iron have been used as solventmetals for making polycrystalline diamond. Platinum and other materialscould also be used for a binder.

[0151] CoCr may be used as a solvent-catalyst metal for sintering PCD toachieve a more wear resistant PDC. Infiltrating diamond particles withCobalt (Co) metal produces standard polycrystalline diamond compact. Asthe cobalt infiltrates the diamond, carbon is dissolved (mainly from thesmaller diamond grains) and reprecipitates onto the larger diamondgrains causing the grains to grow together. This is known as liquidphase sintering. The remaining pore spaces between the diamond grainsare filled with cobalt metal.

[0152] In this example, the alloy Cobalt Chrome (CoCr) may be used asthe solvent metal which acts similarly to Co metal. However, it differsin that the CoCr reacts with some of the dissolved carbon resulting inthe precipitation of CoCr carbides. These carbides, like most carbides,are harder (abrasion resistant) than cobalt metal and results in a morewear or abrasion resistant PDC.

[0153] Other metals can be added to Co to form metal carbides asprecipitates within the pore spaces between the diamond grains. Thesemetals include the following, but not limited to, Ti, W, Mo, V, Ta, Nb,Zr, Si, and combinations thereof.

[0154] It is important not just to add the solvent metal to diamondfeedstock, but also to include solvent metal in an appropriateproportion and to mix it evenly with the feedstock. The use of about 86%diamond feedstock and 15% solvent metal by mass (weight) has providedgood result, other useful ratios of diamond feedstock to solvent metalmay include 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 65:35,75:25, 80:20, 90:10, 95:5, 97:3, 98:2, 99:1, 99.5:0.5, 99.7:0.3,99.8:0.2, 99.9:0.1 and others.

[0155] In order to mix the diamond feedstock with solvent-catalystmetal, first the amounts of feedstock and solvent metal to be mixed maybe placed together in a mixing bowl, such as a mixing bowl made of thedesired solvent-catalyst metal. Then the combination of feedstock andsolvent metal may be mixed at an appropriate speed (such as 200 rpm)with dry methanol and attritor balls for an appropriate time period,such as 30 minutes. The attritor balls, the mixing fixture and themixing bowl may be made from the solvent-catalyst metal. The methanolmay then be decanted and the diamond feedstock separated from theattritor balls. The feedstock may then be dried and cleaned by firing ina molecular hydrogen furnace at about 1000 degrees Celsius for about 1hour. The feedstock is then ready for loading and sintering.Alternatively, it may be stored in conditions which will preserve itscleanliness. Appropriate furnaces which may be used for firing alsoinclude hydrogen plasma furnaces and vacuum furnaces.

[0156] Loading Diamond Feedstock

[0157] Referring to FIG. 3, an apparatus for carrying out a loadingtechnique is depicted. The apparatus includes a spinning rod 301 with alongitudinal axis 302, the spinning rod being capable of spinning aboutits longitudinal axis. The spinning rod 701 has an end 303 matched tothe size and shape of the part to be manufactured. For example, if thepart to be manufactured is non-planar, the spinning rod end 303 may beheminon-planar.

[0158] A compression ring 304 is provided with a bore 305 through whichthe spinning rod 301 may project. A die 306 or can is provided with acavity 307 also matched to the size and shape of the part to be made.

[0159] In order to load diamond feedstock, the spinning rod is placedinto a drill chuck and the spinning rod is aligned with the center pointof the die. The depth to which the spinning rod stops in relation to thecavity of the die is controlled with a set screw and monitored with adial indicator.

[0160] The die is charged with a known amount of diamond feedstockmaterial. The spinning rod is then spun about its longitudinal axis andlowered into the die cavity to a predetermined depth. The spinning rodcontacts and rearranges the diamond feedstock during this operation.Then the spinning of the spinning rod is stopped and the spinning rod islocked in place.

[0161] The compression ring is then lowered around the outside of thespinning rod to a point where the compression ring contacts diamondfeedstock in the cavity of the die. The part of the compression ringthat contacts the diamond is annular. The compression ring is tamped upand down to compact the diamond. This type of compaction is used todistribute diamond material throughout the cavity to the same densityand may be done in stages to prevent bridging. Packing the diamond withthe compaction ring causes the density of the diamond around the equatorof the sample caused to be very uniform and the same as that of thepolar region in the cavity. In this configuration, the diamond sintersin a truly non-planar fashion and the resulting part maintains itssphericity to close tolerances.

[0162] Controlling Large Volumes of Powder Feedstocks, Such As Diamond

[0163] The following information provides further instruction on controland pre-processing of diamond feedstock before sintering.Polycrystalline Diamond Compact (PDC) and Polycrystalline Cubic BoronNitride (PCBN) powders reduce in volume during the sintering process.The amount of shrinkage experienced is dependent on a number of factorssuch as:

[0164] a. The amount of metal mixed with the diamond.

[0165] b. The loading density of the powders.

[0166] c. The bulk density of diamond metal mix.

[0167] d. The volume of powder loaded.

[0168] e. Particle size distribution (PSD) of the powders.

[0169] In most PDC and CBN sintering applications, the volume of powderused is small enough that shrinkage is easily managed, as shown in FIG.3A-1. In FIG. 3A, we can see a can 3A-54 in which can halves 3A-53contain a substrate 3A-52 and a diamond table 3A-51. However, whensintering large volumes of diamond powders in spherical configurations,shrinkage is great enough to cause buckling of the containment cans3A-66 as shown in FIG. 3A-2 and the cross section of FIG. 3A-3. Thediamond has sintered 3A-75 but the can has buckles 3A-77 and wrinkles3A-78, resulting in a non-uniform and damaged part. The following methodis an improved loading, pre-compression, densification, and refractorycan sealing method for spherical and non-planar parts loaded with largevolumes of diamond and/or metal powders. The processing steps aredescribed below.

[0170] Referring to FIG. 3A-4 and its cross section at FIG. 3A-5, PDC orPCBN powders 3A-911 are loaded against a substrate 3A-99 and into arefractory metal containment can 3A-910 having a seal 3A-912. Extrapowder may be loaded normal to the seam in the cans to accommodateshrinkage.

[0171] Referring to FIG. 3A-6, a can assembly 3A-913 is placed intocompaction fixture 3A-1014, which may be a cylindrical holder or slide3A-1015 with two hemispherical punches 3A-1016 and 3A-1017. The fixtureis designed to support the containment cans and allow the cans to slipat the seam during the pressing operation.

[0172] Referring to FIG. 3A-7-1, relationship of the can half skins3A-910 with the junction 3A-912 and the punch 3A-1016 is seen.

[0173] Referring to FIG. 3A-7, fixture 3A-1014 with can 3A-913 is placedinto a press 3A-1218 and the upper and lower punches compress the canassembly. The containment can halves slip past each other preventingbuckling while the powdered feedstock is compressed.

[0174] Referring to FIG. 3A-8, the upper punch is retracted and acrimping die is attached to the cylinder.

[0175] Referring to FIGS. 3A-9 and 3A-9-1, the lower punch is raiseddriving excess can material into the hemispherical portion of thecrimping die folding the excess around the upper can.

[0176] Referring to FIG. 3A-10, the lower punch is raised expelling thecan assembly from the cylinder.

[0177] Referring to FIG. 3A-11, the can assembly emerges from pressingoperation spherical with high loading density. The part can then besintered in a cubic or other press without buckling or breaking thecontainment cans.

[0178] Binding Diamond Feedstock Generally

[0179] Another method which may be employed to maintain a uniformdensity of the feedstock diamond is the use of a binder. A binder isadded to the correct volume of feedstock diamond, and then thecombination is pressed into a can. Some binders which might be usedinclude polyvinyl butyryl, polymethyl methacrylate, polyvinyl formol,polyvinyl chloride acetate, polyethylene, ethyl cellulose,methylabietate, paraffin wax, polypropylene carbonate and polyethylmethacrylate.

[0180] In one embodiment of the devices, the process of binding diamondfeedstock includes four steps. First, a binder solution is prepared. Abinder solution may be prepared by adding about 5 to 25% plasticizer topellets of poly(propylene carbonate), and dissolving this mixture insolvent such as 2-butanone to make about a 20% solution by weight.

[0181] Plasticizers that may be used include nonaqueous bindersgenerally, glycol, dibutyl phthalate, benzyl butyl phthalate, alkylbenzyl phthalate, diethylhexyl phthalate, diisoecyl phthalate,diisononyl phthalate, dimethyl phthalate, dipropylene glycol dibenzoate,mixed glycols dibenzoate, 2-ethylhexyl diphenyl dibenzoate, mixedglycols dibenzoate, 2-ethylhexyl diphenyl phosphate, isodecyl diphenylphosphate, isodecyl diphenl phosphate, tricrestyl phosphate, tributoxyethyl phosphate, dihexyl adipate, triisooctyl trimellitate, dioctylphthalate, epoxidized linseed oil, epoxidized soybean oil, acetyltriethyl citrate, propylene carbonate, various phthalate esters, butylstearate, glycerin, polyalkyl glycol derivatives, diethyl oxalate,paraffin wax and triethylene glycol. Other appropriate plasticizers maybe used as well.

[0182] Solvents that may be used include 2-butanone, methylene chloride,chloroform, 1,2-dichloroethne, trichlorethylene, methyl acetate, ethylacetate, vinyl acetate, propylene carbonate, n-propyl acetate,acetonitrile, dimethylformamide, propionitrile, n-mehyl-2-pyrrolidene,glacial acetic acid, dimethyl sulfoxide, acetone, methyl ethyl ketone,cyclohexanone, oxysolve 80a, caprotactone, butyrolactone,tetrahydrofuran, 1,4 dioxane, propylene oxide, cellosolve acetate,2-methoxy ethyl ether, benzene, styrene, xylene, ethanol, methanol,toluene, cyclohexane, chlorinated hydrocarbons, esters, ketones, ethers,ethyl benzene and various hydrocarbons. Other appropriate solvents maybe used as well.

[0183] Second, diamond is mixed with the binder solution. Diamond may beadded to the binder solution to achieve about a 2-25% binder solution(the percentage is calculated without regard to the 2-butanone).

[0184] Third, the mixture of diamond and binder solution is dried. Thismay be accomplished by placing the diamond and binder solution mixturein a vacuum oven for about 24 hours at about 50 degrees Celsius in orderto drive out all of the solvent 2-butanone. Fourth, the diamond andbinder may be pressed into shape. When the diamond and binder is removedfrom the oven, it will be in a clump that may be broken into pieceswhich are then pressed into the desired shape with a compaction press. Apressing spindle of the desired geometry may be contacted with the bounddiamond to form it into a desired shape. When the diamond and binderhave been pressed, the spindle is retracted. The final density ofdiamond and binder after pressing may be at least about 2.6 grams percubic centimeter.

[0185] If a volatile binder is used, it should be removed from theshaped diamond prior to sintering. The shaped diamond is placed into afurnace and the binding agent is either gasified or pyrolized for asufficient length of time such that there is no binder remaining.Polycrystalline diamond compact quality is reduced by foreigncontamination of the diamond or substrate, and great care must be takento ensure that contaminants and binder are removed during the furnacecycle. Ramp up and the time and temperature combination are critical foreffective pyrolization of the binder. For the binder example givenabove, the debinding process that may be used to remove the binder is asfollows. Reviewing FIG. 4 while reading this description may be helpful.

[0186] First, the shaped diamond and binder are heated to from ambienttemperature to about 500 degrees Celsius. The temperature may beincreased by about 2 degrees Celsius per minute until about 500 degreesCelsius is reached. Second, the temperature of the bound and shapeddiamond is maintained at about 500 degrees Celsius for about 2 hours.Third, the temperature of the diamond is increased again. Thetemperature may be increased from about 500 degrees Celsius by about 4degrees per minute until a temperature of about 950 degrees Celsius isreached. Fourth, the diamond is maintained at about 950 degrees Celsiusfor about 6 hours. Fifth, the diamond is then permitted to return toambient temperature at a temperature decrease of about 2 degrees perminute.

[0187] In some embodiments of the devices, it may be desirable topreform bound diamond feedstock by an appropriate process, such asinjection molding. The diamond feedstock may include diamond crystals ofone or more sizes, solvent-catalyst metal, and other ingredients tocontrol diamond recrystallization and solvent-catalyst metaldistribution. Handling the diamond feedstock is not difficult when thedesired final curvature of the part is flat, convex dome or conical.However, when the desired final curvature of the part has complexcontours, such as illustrated herein, providing uniform thickness andaccuracy of contours of the polycrystalline diamond compact is moredifficult when using powder diamond feedstock. In such cases it may bedesirable to perform the diamond feedstock before sintering.

[0188] If it is desired to perform diamond feedstock prior to loadinginto a can for sintering, rather than placing powder diamond feedstockinto the can, the steps described herein and variations of them may befollowed. First, as already described, a suitable binder is added to thediamond feedstock. Optionally, powdered solvent-catalyst metal and othercomponents may be added to the feedstock as well. The binder willtypically be a polymer chosen for certain characteristics, such asmelting point, solubility in various solvents, and CTE. One or morepolymers may be included in the binder. The binder may also include anelastomer and/or solvents as desired in order to achieve desiredbinding, fluid flow and injection molding characteristics. The workingvolume of the binder to be added to a feedstock may be equal to orslightly more than the measured volume of empty space in a quantity oflightly compressed powder. Since binders typically consist of materialssuch as organic polymers with relatively high CTE's, the working volumeshould be calculated for the injection molding temperatures expected.The binder and feedstock should be mixed thoroughly to assure uniformityof composition. When heated, the binder and feedstock will havesufficient fluid character to flow in high pressure injection molding.The heated feedstock and binder mixture is then injected under pressureinto molds of desired shape. The molded part then cools in the molduntil set, and the mold can then be opened and the part removed.Depending on the final polycrystalline diamond compact geometry desired,one or more molded diamond feedstock component can be created and placedinto a can for polycrystalline diamond compact sintering. Further, useof this method permits diamond feedstock to be molded into a desiredform and then stored for long periods of time prior to use in thesintering process, thereby simplifying manufacturing and resulting inmore efficient production.

[0189] As desired, the binder may be removed from the injection moldeddiamond feedstock form. A variety of methods are available to achievethis. For example, by simple vacuum or hydrogen furnace treatment, thebinder may be removed from the diamond feedstock form. In such a method,the form would be brought up to a desired temperature in a vacuum or ina very low pressure hydrogen (reducing) environment. The binder willthen volatilize with increasing temperature and will be removed from theform. The form may then be removed from the furnace. When hydrogen isused, it helps to maintain extremely clean and chemically activesurfaces on the diamond crystals of the diamond feedstock form.

[0190] An alternative method for removing the binder from the forminvolves utilizing two or polymer (such as polyethylene) binders withdifferent molecular weights. After initial injection molding, thediamond feedstock form is placed in a solvent bath which removes thelower molecular weight polymer, leaving the higher molecular weightpolymer to maintain the shape of the diamond feedstock form. Then thediamond feedstock form is placed in a furnace for vacuum or very lowpressure hydrogen treatment for removal of the higher molecular weightpolymer.

[0191] Partial or complete binder removal from the diamond feedstockform may be performed prior to assembly of the form in a pressureassembly for polycrystalline diamond compact sintering. Alternatively,the pressure assembly including the diamond feedstock form may be placedinto a furnace for vacuum or very low pressure hydrogen furnacetreatment and binder removal.

[0192] Dilute Binder

[0193] In some embodiments, dilute binder may be added to PCD, PCBN orceramic powders to hold form. This technique may be used to provide animproved method of forming Polycrystalline Diamond Compact (PDC),Polycrystalline Cubic Boron Nitride (PCBN), ceramic, or cermet powdersinto layers of various geometries. A PDC, PCBN, ceramic or cermet powdermay be mixed with a temporary organic binder. This mixture may be mixedand cast or calendared into a sheet (tape) of the desired thickness. Thesheet may be dried to remove water or organic solvents. The dried tapemay be then cut into shapes needed to conform to the geometry of acorresponding substrate. The tape/substrate assembly may be then heatedin a vacuum furnace to drive off the binder material. The temperaturemay be then raised to a level where the ceramic or cermet powder fusesto itself and/or to the substrate, thereby producing a uniformcontinuous ceramic or cermet coating bonded to the substrate.

[0194] Referring to FIG. 5, a die 55 with a cup/can in it 54 and diamondfeedstock against it 52 are depicted. A punch 53 is used to form thediamond feedstock into a desired shape. Binder liquid 51 is not added tothe powder until after the diamond, PCBN, ceramic or cermet powder 52 isin the desired geometry. Dry powder 52 is spin formed using a rotatingformed punch 53 in a refectory containment can 54 supported in a holdingdie 55. In another method shown in FIG. 6, feedstock powder 62 is addedto a mold 66. A punch forms the feedstock to shape. A vibrator 67 may beused help the powder 62 take on the shape of the mold 66. After thepowder feedstock is in the desired geometry, a dilute solution of anorganic binder with a solvent is allowed to percolate through the powdergranules.

[0195] As shown in FIGS. 7 and 8, one powder layer 88 can be loaded, andafter a few minutes, when the binder is cured sufficiently at roomtemperature, another layer 89 can be loaded on top of the first layer88. This method is particularly useful in producing PDC or CBN withmultiple layers of varying powder particle size and metal content. Theprocess can be repeated to produce as many layers as desired. FIG. 7shows a section view of a spherical, multi-layered powder load using afirst layer 88, second layer 89, third layer 810, and final layer 811.The binder content should be kept to minimum to produce good loadingdensity and to limit the amount of gas produced during the binderremoval phase to reduce the tendency of the containment cans beingdisplaced from a build up of internal pressure.

[0196] Once al of the powder layers are loaded the binder may beburned-out in a vacuum oven at a vacuum of about 200 Militorrs or lessand at the time and desired temperature profile, such as that shown inFIG. 9. An acceptable binder is 0.5 to 5% propylene carbonate in methylethyl keytone. An example binder burn out cycle that may be used toremove binder is as follows: Time Temperature (minutes) (degreesCentigrade) 0 21 4 100 8 250 60 250 140 800 170 800 290 21

[0197] Gradients

[0198] Diamond feedstock may be selected and loaded in order to createdifferent types of gradients in the diamond table. These include aninterface gradient diamond table, an incremental gradient diamond table,and a continuous gradient diamond table.

[0199] If a single or mix of diamond feedstock is loaded adjacent asubstrate, as discussed elsewhere herein, sweep of solvent-catalystmetal through the diamond will create an interface gradient in thegradient transition zone of the diamond table.

[0200] An incremental gradient diamond table may be created by loadingdiamond feedstocks of differing characteristics (diamond particle size,diamond particle distribution, metal content, etc.) in different strataor layers before sintering. For example, a substrate is selected, and afirst diamond feedstock containing 60% solvent-catalyst metal by weightis loaded in a first strata adjacent the substrate. Then a seconddiamond feedstock containing 40% solvent-catalyst metal by weight isloaded in a second strata adjacent the first strata. Optionally,additional strata of diamond feedstock may be used. For example, a thirdstrata of diamond feedstock containing 20% solvent-catalyst metal byweight may be loaded adjacent the second strata.

[0201] A continuous gradient diamond table may be created by loadingdiamond feedstock in a manner that one or more of its characteristicscontinuously vary from one depth in the diamond table to another. Forexample, diamond particle size may vary from large near a substrate (inorder to create large interstitial spaces in the diamond forsolvent-catalyst metal to sweep into) to small near the diamond surfacein order to create a part that is strongly bonded to the substrate butthat has a very low friction surface.

[0202] The diamond feedstocks of the different strata may be of the sameor different diamond particle size and distribution. Solvent-catalystmetal may be included in the diamond feedstock of the different stratain weight percentages of from about 0% to more than about 80%. In someembodiments, diamond feedstock will be loaded with no solvent-catalystmetal in it, relying on sweep of solvent-catalyst metal from thesubstrate to achieve sintering. Use of a plurality of diamond feedstockstrata, the strata having different diamond particle size anddistribution, different solvent-catalyst metal by weight, or both,allows a diamond table to be made that has different physicalcharacteristics at the interface with the substrate than at the surface.This allows a polycrystalline diamond compact to be manufactured whichhas a diamond table very firmly bonded to its substrate.

[0203] Bisquing Processes to Hold Shapes

[0204] If desired, a bisquing process may be used to hold shapes forsubsequent processing of polycrystalline diamond compacts,polycrystalline cubic boron nitride, and ceramic or cermet products.This involves an interim processing step in High Temperature HighPressure (HTHP) sintering of Polycrystalline Diamond Compact (PDC),Polycrystalline Boron Nitride (PCBN), ceramic, or cermet powders called“bisquing.” Bisquing may provide the following enhancements to theprocessing of the above products:

[0205] a. Pre-sintered shapes can be controlled that are at a certaindensity and size.

[0206] b. Product consistency is improved dramatically.

[0207] c. Shapes can be handled easily in the bisque form.

[0208] d. In layered constructs, bisquing keeps the different layersfrom contaminating each other.

[0209] e. Bisquing different components or layers separately increasethe separation of work elements increasing production efficiency andquality.

[0210] f. Bisquing molds are often easer to handle and manage prior tofinal assembly that the smaller final product forms.

[0211] Bisquing molds or containers can be fabricated from any hightemperature material that has a melting point higher than the highestmelting point of any mix component to be bisque. Bisque mold/containermaterials that work well are Graphite, Quartz, Solid Hexagonal BoronNitride (HBN), and ceramics. Some refractory type metals (Hightemperature stainless steels, Nb, W, Ta, Mo, etc) work well is someapplications where bisquing temperatures are lower and sticking of thebisque powder mix is not a problem. Molds or containers can be shaped bypressing, forming, or machining, and are preferably polished at theinterface between the bisque material and the mold/container itself.Some mold/container materials glazing and/or firing prior to use.

[0212]FIG. 10 shows an embodiment 1006 for making a cylinder with aconcave relief or trough using the bisquing process. Pre-mixed powdersof PDC, PCBN, ceramic, or cermet materials 1001 which contain enoughmetal to undergo solid phase sintering are loaded into the bisquingmolds or containers 1002 and 1004. A release agent may be requiredbetween the mold/container to ensure that the final bisque form can beremoved following furnace firing. Some release agents that may be usedare HBN, Graphite, Mica, and Diamond Powder. A bisque mold/container lidwith an integral support form 1005 is placed over the loaded powdermaterial to ensure that the material holds form during the sinteringprocess. The bisque mold/container assembly is then placed in a hydrogenatmosphere furnace, or alternately, in a vacuum furnace which is drawnto a vacuum ranging from 200 to 0 Militorrs. The load is then heatedwithin a range of 0.6 to 0.8 of the melting temperature of the largestvolume mix metal. A typical furnace cycle is shown in FIG. 12. Once thefurnace cycle is completed and the mold/container is cooled, thehardened bisque formed powders can be removed for further HPHTprocessing. A bisque form of feedstock 1003 is the net product.

[0213]FIG. 11 shows fabrication 1110 of a bisque form for a fullhemispherical part 1109 that has multiple powder layers 1107 a and 1107b. Pre-mixed powders of PDC, PCBN, ceramic, or cermet materials whichcontain enough metal to undergo solid phase sintering are loaded intothe bisquing molds or containers. A release agent may be requiredbetween the mold/container to ensure that the final bisque form can beremoved following furnace firing. The bisque mold/container assembly maythen placed in a vacuum furnace which is drawn to a vacuum ranging from200 to 0 Militorrs. The load is then heated within a range of 0.6 to 0.8of the melting temperature of the largest volume mix metal. Once thefurnace cycle is completed and the mold/container is cooled, thehardened bisque 1109 formed powders can be removed for further HPHTprocessing. An example of a bisque binder burn-out cycle that may beused to remove the unwanted materials before sintering is as follows:Time Temperature (hours) (degrees Centigrade) 0 21 0.25 21 5.19 800 6.19800 10.19 21

[0214] Reduction of Free Volume in Diamond Feedstock

[0215] As mentioned earlier, it may be desirable to remove free volumein the diamond feedstock before sintering is attempted. This may be auseful procedure especially when producing non-planar concave and convexparts. If a press with sufficient anvil travel is used for high pressureand high temperature sintering, however, this step may not be necessary.Free volume in the diamond feedstock may in some instances be reduced sothat the resulting diamond feedstock is at least about 95% theoreticaldensity and sometimes closer to about 97% of theoretical density.

[0216] Referring to FIGS. 13 and 14, an assembly used for precompressingdiamond to eliminate free volume is depicted. In the drawing, thediamond feedstock is intended to be used to make a convex non-planarpolycrystalline diamond part. The assembly may be adapted forprecompressing diamond feedstock for making polycyrstalline diamondcompacts of other complex shapes.

[0217] The assembly depicted includes a cube 1301 of a pressure transfermedium. A cube is made from pyrophillite or other appropriate pressuretransfer material such as a synthetic pressure medium and is intended toundergo pressure from a cubic press with anvils simultaneously pressingthe six faces of the cube. A cylindrical cell rather than a cube wouldbe used if a belt press were utilized for this step.

[0218] The cube 801 has a cylindrical cavity 1302 or passage through it.The center of the cavity 1302 will receive a non-planar refractory metalcan 1310 loaded with diamond feedstock 806 that is to be precompressed.The diamond feedstock 1306 may have a substrate with it.

[0219] The can 1310 consists of two heminon-planar can halves 1310 a and1310 b, one of which overlaps the other to form a slight lip 1312. Thecan may be an appropriate refractory metal such as niobium, tantalum,molybdenum, etc. The can is typically two hemispheres, one which isslightly larger to accept the other being slid inside of it to fullyenclosed the diamond feedstock. A rebated area or lip is provided in thelarger can so that the smaller can will satisfactorily fit therein. Theseam of the can is sealed with an appropriate sealant such as dryhexagonal boronitride or a synthetic compression medium. The sealantforms a barrier that prevents the salt pressure medium from penetratingthe can. The can seam may also be welded by plasma, laser, or electronbeam processes.

[0220] An appropriately shaped pair of salt domes 1304 and 1307 surroundthe can 1310 containing the diamond feedstock 1306. In the exampleshown, the salt domes each have a heminon-planar cavity 1305 and 1308for receiving the can 1310 containing the non-planar diamond feedstock1306. The salt domes and the can and diamond feedstock are assembledtogether so that the salt domes encase the diamond feedstock. A pair ofcylindrical salt disks 1303 and 1309 are assembled on the exterior ofthe salt domes 1304 and 1307. All of the aforementioned components fitwithin the bore 1302 of the pressure medium cube 1301.

[0221] The entire pyrocube assembly is placed into a press andpressurized under appropriate pressure (such as about 40-68 Kbar) andfor an appropriate although brief duration to precompress the diamondand prepare it for sintering. No heat is necessary for this step.

[0222] Mold Releases

[0223] When making non-planar shapes, it may be desirable to use a moldin the sintering process to produce the desired net shape. CoCr metalmay used as a mold release in forming shaped diamond or other superhardproducts. Sintering the superhard powder feed stocks to a substrate, theobject of which is to lend support to the resulting superhard table, maybe utilized to produce standard Polycrystalline Diamond Compact (PDC)and Polycrystalline Cubic Boron Nitride (PCBN) parts. However, in someapplications, it is desired to remove the diamond table from thesubstrate.

[0224] Referring to FIG. 14, a diamond layer 1402 and 1403 has beensintered to a substrate 1401 at an interface 1404. The interface 1404must be broken to result in free standing diamond if the substrate isnot required in the final product. A mold release may be used to removethe substrate from the diamond table. If CoCr alloy is used for thesubstrate, then the CoCr itself serves as a mold release, as well asserving as a solvent-catalyst metal. CoCr works well as a mold releasebecause its Coefficient of Thermal Expansion (CTE) is dramaticallydifferent than that of sintered PDC or PCBN 3. Because of the largedisparity in the CTE's between PDC and PCBN and CoCr, high stress isformed at the interface 1501 between these two materials as shown inFIG. 15. The stress that is formed is greater than the bond energybetween the two materials. When the stress is greater than the bondenergy, a crack is formed at the point of highest stress. The crack thenpropagates following the narrow region of high stress concentrated atthe interface. Referring to FIG. 16, in this way, the CoCr substrate1601 will separate from the PCD or PCBN 1602 that was sintered aroundit, regardless of the shape of the interface.

[0225] Materials other than CoCr can be used as a mold release. Thesematerials include those metals with high CTE's and, in particular, thosethat are not good carbide formers. These are, for example, Co, Ni, CoCr,CoFe, CoNi, Fe, steel, etc.

[0226] Gradient Layers and Stress Modifiers

[0227] Gradient layers and stress modifiers may be used in the making ofsuperhard constructs. Gradient layers may be used to achieve any of thefollowing objectives:

[0228] a. Improve the “sweep” of solvent metal into the outer layer ofsuperhard material and to control the amount of solvent metal introducedfor sintering into said outer layer.

[0229] b. Provide a “sweep” source to flush out impurities for depositon the surface of the outer layer of superhard material and/or chemicalattachment/combination with the refractory containment cans.

[0230] c. Control the Bulk Modulus of the various gradient layers andthereby control the overall dilatation of the construct during thesintering process.

[0231] d. Affect the “Coefficient of Thermal Expansion” (CTE) of each ofthe various layers by changing the ratio of metal or carbides todiamond, PCBN or other Superhard materials to reduce the CTE of anindividual gradient layer.

[0232] e. Allow for the control of structural stress fields through thevarious levels of gradient layers to optimize the overall construct.

[0233] f. Change the direction of stress tensors to improve the outerSuperhard layer, e.g., direct the tensor vectors toward the center of aspherical construct to place the outer layer diamond into compression,or conversely, direct the tensor vectors from the center of theconstruct to reduce interface stresses between the various gradientlayers.

[0234] g. Improve the overall structural stress compliance to externalor internal loads by providing a construct that has substantiallyreduced brittleness and increased toughness wherein loads aretransferred through the construct without crack initiation andpropagation.

[0235] Referring to FIG. 17, The liquid sintering phase ofPolycrystalline Diamond (PDC) and Polycrystalline Cubic Boron Nitride(PCBN) is typically accomplished by mixing the solvent sintering metal1701 directly with the Diamond or PCBN powders 1702 prior to the “HighTemperature High Pressure (HPHT) pressing, or (referring to FIG. 18)“sweeping” the solvent metal 1802 from a substrate 1801 into feedstockpowders from the adjacent substrate during HPHT. The very best highquality PDC or PCBN is created using the “sweep” process.

[0236] There are several theories related to the increased PDC and CBHquality when using the sweep method. However, most of those familiarwith the field agree that allowing the sintering metal to “sweep” fromthe substrate material provides a “wave front” of sintering metal thatquickly “wets” and dissolves the diamond or CBN and uses only as muchmetal as required to precipitate Diamond or PCBN particle-to-particlebonding. Whereas in a “premixed” environment the metal “blinds off” theparticle-to particle reaction because too much metal is present, orconversely, not enough metal is present to ensure the optimal reaction.

[0237] Furthermore, it is felt that the “wave front” of metal sweepingthrough the powder matrix also carries away impurities that wouldotherwise impede the formation of high quality PDC of PCBN. Theseimpurities are normally “pushed” ahead of the sintering metal “wavefront” and are deposited in pools adjacent to the refractory containmentcans. FIG. 19 depicts the substrate 1904, the wavefront 1903, and thefeedstock crystals or powder 1902 which the wavefront will sweep through1901. Certain refractory material such as Niobium, Molybdenum, andZirconium can act as “getters” which combine with the impurities as theyimmerge from the matrix giving additional assistance in the creation ofhigh quality end products.

[0238] While there are compelling reasons to use the “sweep” process insintering PDC and PCBN there are also problems that arise out of itsuse. For example, not all substrate metals are as controllable as othersas to the quantity of material that is delivered and ultimately utilizedby the powder matrix during sintering. Cobalt metal (6 to 13% by volume)sweeping from cemented tungsten carbide is very controllable when usedagainst diamond or PCBN powders ranging from 1 to 40 microns particlesized. On the other hand, Cobalt Chrome Molybdenum (CoCrMo) that isuseful as a solvent metal to make PDC for some applications overwhelmsthe same PDC matrix with CoCrMo metal in a pure sweep process sometimesproducing inferior quality PDC. The fact that the CoCrMo has a lowermelting point than cobalt, and further that there is an inexhaustiblesupply when using a solid CoCrMo substrate adjacent to the PDC matrix,creates a non-controllable processing condition.

[0239] In some applications where it is necessary to use sinteringmetals such a CoCrMo that can not be “swept” from a cemented carbideproduct, it is necessary to provide a simulated substrate against thePDC powders that provides a controlled release and limited supply ofCoCrMo for the process.

[0240] These “simulated” substrates have been developed in the forms of“gradient” layers of mixtures of diamond, carbides, and metals toproduce the desired “sweep” affect for sintering the outer layer of PDC.The first “gradient layer” (just adjacent to the outer or primarydiamond layer which will act as the bearing or wear surface) can beprepared using a mixture of Diamond, Cr₃C₂, and CoCrMo. Depending of thesize fraction of the diamond powder used in the outer layer, the firstgradient layers diamond size fraction and metal content is adjusted forthe optimal sintering conditions.

[0241] Where a “simulated” substrate is used, it has been discoveredthat often a small amount of solvent metal, in this case CoCrMo must beadded to the outside diamond layer as catalyst to “kick-off” thesintering reaction.

[0242] One embodiment utilizes the mix ranges for the outer 2001 andinner 2002 gradient layers of FIG. 20 that are listed in Table 9. TABLE9 DIAMOND DIAMOND Cr₃C₂ CoCrMo GRADIENT (Vol. (Size (Vol. (Vol. LAYERSPercent) Fraction-μm) Percent) Percent) Outer 92 25 0 8 Inner 70 40 1020

[0243] The use of gradient layers with solid layers of metal allows thedesigner to match the Bulk Modulus to the Coefficient of ThermalExpansion (CTE) of various features of the construct to counteractdilatory forces encountered during the HTHP phase of the sinteringprocess. For example, in a spherical construct as the pressure increasesthe metals in the construct are compressed or dilated radially towardthe center of the sphere. Conversely, as the sintering temperatureincreases the metal expands radially away from the center of the sphere.Unless these forces are balanced in some way, the compressive dilatoryforces will initiate cracks in the outer diamond layer and cause theconstruct to be unusable.

[0244] Typically, changes in bulk modulus of solid metal features in theconstruct are controlled by selecting metals with a compatible modulusof elasticity. The thickness and other sizing features are alsoimportant. CTE, on the other hand, is changed by the addition of diamondor other carbides to the gradient layers.

[0245] One embodiment, depicted in FIG. 21, involves the use of twogradient outer layers 2101 and 2102, a solid titanium layer 2103 and aninner CoCrMo sphere 2104. In this embodiment the first gradient layerprovides a “sweep source” of biocompatible CoCrMo solvent metal to theouter diamond layer. The solid Titanium layer provides a dilatory sourcethat offsets the CTE from the solid CoCrMo center ball and keeps it from“pulling away” from the Titanium/CoCrMo interface as the sinteringpressure and temperature go from the 65 Kbar and 1400° C. sinteringrange to 1 bar and room temperature.

[0246] Where two or more powder based gradient layers are to be used inthe construct it becomes increasingly important to control the CTE ofeach layer to ensure structural integrity following sintering. Duringthe sintering process stresses are induced along the interface betweeneach of the gradient layers. These high stresses are a direct result ofthe differences in the CTE between any two adjacent layers. To reducethese stresses one or both of the layer materials CTE's must bemodified.

[0247] The CTE of the a substrate can be modified by either changing toa substrate with a CTE close to that of diamond (an example is the useof cemented Tungsten Carbide, where the CTE of Diamond is approximately1.8 μm/m-° C. and Cemented Tungsten Carbide is Approximately 4.4 μm/m-°C)., or in the case of powdered layers, by adding a low CTE material tothe substrate layer itself. That is, making a mixture of two or morematerials, one or more of which will alter the CTE of the substratelayer.

[0248] Metal powders can be mixed with diamond or other superhardmaterials to produce a material with a CTE close to that of diamond andthus produce stresses low enough following sintering to preventdelamination of the layers at their interfaces. Experimental data showsthat the CTE altering materials will not generally react with eachother, which allows the investigator to predict the outcome of theintermediate CTE for each gradient level.

[0249] The desired CTE is obtained by mixing specific quantities of twomaterials according to the rule of mixtures. Table 10 shows the changein CTE between two materials, A and B as a function of composition(Volume Percent). In this example, materials A and B have CTE's of 150and 600 μIn./In.-° F. respectively. By adding 50 mol % of A to 50 mol %of B the resulting CTE is 375 μin/in-° F.

[0250] One or more of the following component processes is incorporatedinto the mold release system:

[0251] 1) An intermediate layer of material between the polycrystallinediamond compact part and the mould that prevents bonding of thepolycrystalline diamond compact to the mould surface.

[0252] 2) A mold material that does not bond to the polycrystallinediamond compact under the conditions of synthesis.

[0253] 3) A mold material that, in the final stages of, or at theconclusion of, the polycrystalline diamond compact synthesis cycleeither contracts away from the polycrystalline diamond compact in thecase of a net concave polycrystalline diamond compact geometry, orexpands away from the polycrystalline diamond compact in the case of anet convex polycrystalline diamond compact geometry.

[0254] 4) The mold shape can also act, simultaneously as a source ofsweep metal useful in the polycrystalline diamond compact synthesisprocess.

[0255] As an example, a mold release system may be utilized inmanufacturing a polycrystalline diamond compact by employing a negativeshape of the desired geometry to produce heminon-planar parts. The moldsurface contracts away from the final net concave geometry, the moldsurface acts as a source of solvent-catalyst metal for thepolycrystalline diamond compact synthesis process, and the mold surfacehas poor bonding properties to polycrystalline diamond compacts. TABLE10 PREDICTED DIMENSIONAL CHANGES IN AN EIGHT INCH LAYERED CONSTRUCT CTETotal Length Final A % B % (μ In./In-° F.) Change (In.) Dimension (In.)100 0 150 .0012 7.9988 90 10 195 .0016 7.9984 80 20 240 .0019 7.9981 7030 285 .0023 7.9977 60 40 330 .0026 7.9974 50 50 375 .0030 7.9970 40 60420 .0034 7.9966 30 70 465 .0037 7.9963 20 80 510 .0041 7.9959 10 90 555.0044 7.9956 0 100 600 .0048 7.9952

[0256] Referring to FIG. 22, an illustration of how the above CTEmodification works in a one-dimensional example. The one-dimensionalexample works as well in a three-dimensional construct. If the abovematerials A and B are packed in alternating layers 2201 and 2202 asshown in FIG. 22, separately in their pure forms, with their CTE's of150 and 600 μIn./In.-° F. respectively, they will contract exactly 150μIn./In.-° F. and 600 μIn./In.-° F. for every degree decrease intemperature. For an eight inch block of the one inch thick stackedlayers the total change in dimension for a one degree decrease intemperature will be:

[0257] Material A: (4×1 In.)×(0.00015 In./In.-° F.)×1° F.=0.0006 In.

[0258] Material B: (4×1 In.)×(0.00060 In./In.-° F.)×1)° F.=0.0024 In.

[0259] Total overall length decrease in eight inches=0.0030 In.

[0260] By comparison, each of the layers is modified by using a mixtureof 50% of A and 50% of B, and all eight layers are stacked into theeight-inch block configuration shown in FIG. 7. Re-calculation of theoverall length decrease using the new composite CET of 375 μIn./In.-° F.from Table 11 shows:

[0261] Material A+B: (8×1 In.)×(0.000375 In./In.-° F.)×1° F.=0.0030 In.

[0262] Total overall length decrease in eight inches=0.0030 In.

[0263] The length decrease in this case was accurately predicted for theone-dimensional construct using one-inch thick layers by using the Ruleof Mixtures.

[0264] Metals have very high CTE values as compared to diamond, whichhas one of the lowest CTE's of any known material. When metals are usedas substrates for PDC and PCBN sintering considerable stress isdeveloped at the interface. Therefore, mixing low CTE material with thebiocompatible metal for medical implants can be used to reduceinterfacial stresses. One of the best candidate materials is diamonditself. Other materials include refractory metal carbides and bitrides,and some oxides. Borides and suicides would also be good materials froma theoretical standpoint, but may not be biocompatible. The following isa list of candidate materials: Carbides Suicides Oxynitrides NitridesOxides Oxyborides Borides Oxycarbides Carbonitrides

[0265] There are other materials and combinations of materials thatcould be utilized as CTE modifiers.

[0266] There are also other factors that also apply to the reduction ofinterface stresses for a particular geometrical construct. The thicknessof the gradient layer, its position in the construct, and the generalshape of the final construct all contribute in interfacial stress tensorreduction. Geometries that are more spherical tend to promote interfacecircumferential failures from positive or negative radial tensors whilegeometries of a cylindrical configuration tend to fail at the layerinterfaces precipitated by bending stress couples.

[0267] The design of the gradient layers respecting CTE and the amountof contraction the each individual layer will experience during coolingform the HTHP sintering process will largely dictate the direction ofstress tensors in the construct. Generally, the designer will alwaysdesire to have the outer wear layer of superhard material in compressionto prevent delamination and crack propagation. In spherical geometriesthe stress tensors would be directed radially toward the center of thespherical shape giving special attention to the interfacial stresses ateach layer interface to prevent failures at these interfaces as well. Incylindrical geometries the stress tensors would be adjusted to preventstress couples from initiating cracks in either end of the cylinder,especially at the end where the wear surface is present.

[0268] The following are embodiments that relates to a sphericalgeometry wherein combinations of gradient layers and/or solid metalballs are used to control the final outcomes of the constructs. FIG. 23is an embodiment that shows a spherical construct, which utilizes fivegradient layers wherein the composition of each layer is described inTables 11 and 12: TABLE 11 DIAMOND Cr3C2 CoCrMo LAYER LAYER Size (μm)Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 92 8 0.090 2301 Second 2302 40 70 20 20 .104 Third 2303 70 60 20 20 .120 Forth2304 70 60 26 26 .138 Fifth 2305 70 25 37.5 37.5 .154

[0269] TABLE 12 DIAMOND Cr3C2 CoCrMo LAYER LAYER Size (μm) Volume %Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 100 0 0 .0902301 Second 2302 40 70 20 20 .104 Third 2304 70 60 20 20 .120 Forth 230470 60 26 26 .138 Fifth 2305 70 25 37.5 37.5 .154

[0270]FIG. 24 is an embodiment that shows a spherical construct, whichutilizes four gradient layers wherein the composition of each layer isdescribed in Tables 13 and 14. TABLE 13 DIAMOND Cr3C2 CoCrMo LAYER LAYERSize (μm) Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer)20 92 0 8 .097 2401 Second 2402 40 70 10 20 .125 Third 2403 70 60 20 20.144 Forth 2404 70 50 25 25 .240

[0271] TABLE 14 DIAMOND Cr3C2 CoCrMo LAYER LAYER Size (μm) Volume %Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 100 0 0 .0972401 Second 2402 40 70 10 20 .125 Third 2403 70 60 20 20 .144 Forth 24O470 50 25 25 .240

[0272]FIG. 25 shows an embodiment construct that utilizes a centersupport ball with gradient layers laid up on the ball and each other toform the complete construct. The inner ball of solid metal CoCrMo isencapsulate with a 0.003 to 0.010 inch thick refractory barrier can toprevent the over saturation of the system with the ball metal during theHTHP phase of sintering. The composition of each layer is described inTables 15 and 16. TABLE 15 DIAMOND Cr3C2 CoCrMo LAYER LAYER Size (μm)Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 92  0 8 .097 2501 Second 2502 40 70 10 20 .125 Third 2503 70 60 20 20 .144CoCrMo Ball 2504 N/A N/A N/A N/A N/A

[0273] TABLE 16 DIAMOND Cr3C2 CoCrMo LAYER LAYER Size (μm) Volume %Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 100 0 0 .0972501 Second 2502 40 70 10 20 .125 Third 25O3 70 60 20 20 .144 CoCrMoBall 2504 N/A N/A N/A N/A N/A

[0274] Predicated on the end use function of the sphere above, the innerball could be made of Cemented Tungsten Carbide, Niobium, Nickel,Stainless steel, Steel, or one of several other metal or ceramicmaterials to suite the designers needs.

[0275] Embodiments relating to dome shapes are described as follow:

[0276]FIG. 26 shows a dome embodiment construct that utilizes twogradient layers 2601 and 2602 wherein the composition of each layer isdescribed in Tables 17 and 18. TABLE 17 DIAMOND Cr3C2 CoCrMo TiCTiNLAYER LAYER Size (μm) Volume % Volume % Volume % Volume % THICKNESS(In.) First (Outer Layer) 20 94 0 6 0.05 .200 2602 Second 2601 70 60 2020 0.05 .125

[0277] TABLE 18 DIAMOND Cr3C2 CoCrMo TiCTiN LAYER LAYER Size (μm) Volume% Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 1000 0 0.05 .200 2602 Second 2601 70 60 20 20 0.05 .125

[0278]FIG. 27 shows a dome embodiment construct that utilizes twogradient layers 2701 and 2702 wherein the composition of each layer isdescribed in Tables 19 and 20: TABLE 19 DIAMOND Cr3C2 CoCrMo TiCTiNLAYER LAYER Size (μm) Volume % Volume % Volume % Volume % THICKNESS(In.) First (Outer Layer) 20 94 0 6 0.05 .128 2702 Second 2701 70 60 2020 0.05 .230

[0279] TABLE 20 DIAMOND Cr3C2 CoCrMo TiCTiN LAYER LAYER Size (μm) Volume% Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 1000 0 0.05 .128 2702 Second 2701 70 60 20 20 0.05 .230

[0280]FIG. 28 shows a dome embodiment construct that utilizes threegradient layers 2801, 2802 and 2803 where the composition of each layeris described in Tables 21 and 22: TABLE 21 DIAMOND Cr3C2 CoCrMo TiCTiNLAYER LAYER Size (μm) Volume % Volume % Volume % Volume % THICKNESS(In.) First (Outer Layer) 20 96 0 4 0.05 .168 2801 Second 2802 40 80 1010 0.05 .060 Third 2803 70 60 20 20 0.05 .130

[0281] TABLE 22 DIAMOND Cr3C2 CoCrMo TiCTiN LAYER LAYER Size (μm) Volume% Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 1000 0 0.05 .168 2801 Second 2802 40 80 10 10 0.05 .060 Third 2803 70 60 2020 0.05 .130

[0282]FIG. 29 shows a dome embodiment construct that utilizes threegradient layers 2901, 2902 and 9803 wherein the composition of eachlayer is described in Tables 23 and 24: TABLE 23 DIAMOND Cr3C2 CoCrMoTiCTiN LAYER LAYER Size (μm) Volume % Volume % Volume % Volume %THICKNESS (In.) First (Outer Layer) 20 96 0 4 0.05 .065 2901 Second 290240 80 10 10 0.05 .050 Third 2903 70 60 20 20 0.05 .243

[0283] TABLE 24 DIAMOND Cr3C2 CoCrMo TiCTiN LAYER LAYER Size (μm) Volume% Volume % Volume % Volume % THICKNESS (In.) First (Outer Layer) 20 1000 0 0.05 .065 2901 Second 2902 40 80 10 10 0.05 .050 Third 2903 70 60 2020 0.05 .243

[0284] Embodiments relating to Flat Cylindrical shapes are described asfollows:

[0285]FIG. 30 shows a flat cylindrical embodiment construct thatutilizes two gradient layers 3001 and 3002 wherein the composition ofeach layer is described in Tables 25 and 26: TABLE 25 DIAMOND Cr3C2CoCrMo TiCTiN LAYER LAYER Size (μm) Volume % Volume % Volume % Volume %THICKNESS (In.) First (Outer Layer) 20 94 0 6 0.05 3001 Second 3002 7060 20 20 0.05

[0286] TABLE 26 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 3001 Second 3002 70 60 20 20 0.05

[0287]FIG. 31 shows a flat cylindrical embodiment construct thatutilizes three gradient layers 3101, 3102, 3103 wherein the compositionof each layer is described in Tables 27 and 28: TABLE 27 LAYER DIAMONDCr3C2 CoCrMo TiCTiN THICKNESS LAYER Size (μm) Volume % Volume % Volume %Volume % (In.) First (Outer Layer) 20 96 0 4 0.05 3101 Second 3102 40 8010 10 0.05 Third 3103 70 60 20 20 0.05

[0288] TABLE 28 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 3101 Second 3102 40 80 10 10 0.05 Third 3103 70 60 20 200.05

[0289]FIG. 32 shows a flat cylindrical embodiment construct thatutilizes three gradient layers 3201, 3202, 3203 laid up on a CoCrMosubstrate 3204. The cylindrical substrate of solid metal CoCrMo isencapsulate with a 0.003 to 0.010 inch thick refractory barrier can 3205to prevent the over saturation of the system with the substrate metalduring the HTHP phase of sintering. The composition of each layer isdescribed in Tables 29 and 30: TABLE 29 LAYER DIAMOND Cr3C2 CoCrMoTiCTiN THICKNESS LAYER Size (μm) Volume % Volume % Volume % Volume %(In.) First (Outer Layer) 20 96  0  4 0.05 3201 Second 3202 40 80 10 100.05 Third3203 70 60 20 20 0.05 CoCrMo Substrate N/A N/A N/A N/A N/A3204

[0290] TABLE 30 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 3201 Second 3202 40 80 10 10 0.05 Third 3203 70 60 20 200.05 CoCrMo Substrate N/A N/A N/A N/A N/A 3204

[0291] Predicated on the end use function of the cylinder shape of FIG.32 the inner substrate could be made of Cemented Tungsten Carbide,Niobium, Nickel, Stainless steel, Steel, or one of several other metalor ceramic materials to suite the designers needs.

[0292] Embodiments relating to Flat Cylindrical Shapes withFormed-in-Place Concave Features are described as follow:

[0293]FIG. 33 show an embodiment of a flat cylindrical shape with aformed in place concave trough 3303 that utilizes two gradient layers3301 and 3302 wherein the composition of each layer is described inTables 31 and 32: TABLE 31 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESSLAYER Size (μm) Volume % Volume % Volume % Volume % (In.) First (OuterLayer) 20 94 0 6 0.05 .156 3301 Second 3302 70 60 20 20 0.05 .060 FillerSupport 3303 70 60 20 20 0.05 N/A

[0294] TABLE 32 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 .156 3301 Second 3302 70 60 20 20 0.05 .060 Filler Support3303 70 60 20 20 0.05 N/A

[0295]FIG. 34 shows an embodiment of a flat cylindrical shape with aformed in place concave trough 3402 that utilizes two gradient layers3401 and 3402 wherein the composition of each layer is described inTables 33 and 34: TABLE 33 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESSLAYER Size (μm) Volume % Volume % Volume % Volume % (In.) First (OuterLayer) 20 94 0 6 0.05 .156 3401 Second 3402 70 60 20 20 0.05 .060 FillerSupport 3403 70 60 20 20 0.05 N/A

[0296] TABLE 34 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 .156 3401 Second 3402 70 60 20 20 0.05 .060 Filler Support3403 70 60 20 20 0.05 N/A

[0297]FIG. 35 shows an embodiment of a flat cylindrical shape with aformed in place concave 3504 trough that utilizes three gradient layers3501, 3502, 2503 wherein the composition of each layer is described inTables 35 and 36: TABLE 35 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESSLAYER Size (μm) Volume % Volume % Volume % Volume % (In.) First (OuterLayer) 20 96 0 4 0.05 .110 3501 Second 3502 40 80 10 10 0.05 .040 Third2503 70 60 20 20 0.05 .057 Filler Support 3504 70 60 20 20 0.05 N/A

[0298] TABLE 36 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 .110 3501 Second 3502 40 80 10 10 0.05 .040 Third 3503 7060 20 20 0.05 .057 Filler Support 3504 70 60 20 20 0.05 N/A

[0299]FIG. 36 shows an embodiment of a flat cylindrical shape with aformed in place concave trough 3604 that utilizes three gradient layers3601, 3602, 3603 wherein the composition of each layer is described inTables 37 and 38: TABLE 37 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESSLAYER Size (μm) Volume % Volume % Volume % Volume % (In.) First (OuterLayer) 20 96 0 4 0.05 .110 3601 Second 3602 40 80 10 10 0.05 .040 Third3603 70 60 20 20 0.05 .057 Filler Support 3604 70 60 20 20 0.05 N/A

[0300] TABLE 38 LAYER DIAMOND Cr3C2 CoCrMo TiCTiN THICKNESS LAYER Size(μm) Volume % Volume % Volume % Volume % (In.) First (Outer Layer) 20100 0 0 0.05 .110 3601 Second 3602 40 80 10 10 0.05 .040 Third 3603 7060 20 20 0.05 .057 Filler Support 3604 70 60 20 20 0.05 N/A

[0301] Prepare Heater Assembly

[0302] In order to sinter the assembled and loaded diamond feedstockdescribed above into polycrystalline diamond, both heat and pressure arerequired. Heat is provided electrically as the part undergoes pressurein a press. A heater assembly is used to provide the required heat.

[0303] A refractory metal can containing loaded and precompresseddiamond feedstock is placed into a heater assembly. Salt domes are usedto encase the can. The salt domes used may be white salt (NaCl) that isprecompressed to at least about 90-95% of theoretical density. Thisdensity of the salt is desired to preserve high pressures of thesintering system and to maintain geometrical stability of themanufactured part. The salt domes and can are placed into a graphiteheater tube assembly. The salt and graphite components of the heaterassembly may be baked in a vacuum oven at greater than 100 degreesCelsius and at a vacuum of at least 23 torr for about 1 hour in order toeliminate adsorped water prior to loading in the heater assembly. Othermaterials which may be used in construction of a heater assembly includesolid or foil graphite, amorphous carbon, pyrolitic carbon, refractorymetals and high electrical resistant metals.

[0304] Once electrical power is supplied to the heater tube, it willgenerate heat required for polycrystalline diamond formation in the highpressure/high temperature pressing operation.

[0305] Preparation of Pressure Assembly for Sintering

[0306] Once a heater assembly has been prepared, it is placed into apressure assembly for sintering in a press under high pressure and hightemperature. A cubic press or a belt press may be used for this purpose,with the pressure assembly differing somewhat depending on the type ofpress used. The pressure assembly is intended to receive pressure from apress and transfer it to the diamond feedstock so that sintering of thediamond may occur under isostatic conditions.

[0307] If a cubic press is used, then a cube of suitable pressuretransfer media such as pyrophillite will contain the heater assembly.Cell pressure medium would be used if sintering were to take place in abelt press. Salt may be used as a pressure transfer media between thecube and the heater assembly. Thermocouples may be used on the cube tomonitor temperature during sintering. The cube with the heater assemblyinside of it is considered a pressure assembly, and is place into apress a press for sintering.

[0308] Sintering of Feedstock into Polycrystalline Diamond

[0309] The pressure assembly described above containing a refractorymetal can that has diamond feedstock loaded and precompressed within isplaced into an appropriate press. The type of press used at the time ofthe devices may be a cubic press (i.e., the press has six anvil faces)for transmitting high pressure to the assembly along 3 axes from sixdifferent directions. Alternatively, a belt press and a cylindrical cellcan be used to obtain similar results. Other presses may be used aswell. Referring to FIG. 37, a representation of the 6 anvils of a cubicpress 3720 is provided. The anvils 3721, 3722, 3723, 3724, 3725 and 3726are situated around a pressure assembly 3730.

[0310] To prepare for sintering, the entire pressure assembly is loadedinto a press and initially pressurized to about 40-68 Kbars. Thepressure to be used depends on the product to be manufactured and mustbe determined empirically. Then electrical power may be added to thepressure assembly in order to reach a temperature in the range of lessthan about 1145 or 1200 to more than about 1500 degrees Celsius. About5800 watts of electrical power may be used at two opposing anvil faces,creating the current flow required for the heater assembly to generatethe desired level of heat. Once the desired temperature is reached, thepressure assembly is subjected to pressure of about 1 million pounds persquare inch at the anvil face. The components of the pressure assemblytransmit pressure to the diamond feedstock. These conditions may bemaintained for about 3-12 minutes, but could be from less than 1 minuteto more than 30 minutes. The sintering of polycrystalline diamondcompacts takes place in an isostatic environment where the pressuretransfer components are permitted only to change in volume but are notpermitted to otherwise deform. Once the sintering cycle is complete,about a 90 second cool down period is allowed, and then pressure isremoved. The polycrystalline diamond compact is then removed forfinishing.

[0311] Removal of a sintered polycrystalline diamond compact having acurved, compound or complex shape from a pressure assembly is simple dueto the differences in material properties between diamond and thesurrounding metals in some embodiments of the devices. This is generallyreferred to as the mold release system of the devices.

[0312] Removal of Solvent-Catalyst Metal from PCD

[0313] If desired, the solvent-catalyst metal remaining in interstitialspaces of the sintered polycrystalline diamond may be removed. Suchremoval is accomplished by chemical leaching as is known in the art.After solvent-catalyst metal has been removed from the interstitialspaces in the diamond table, the diamond table will have greaterstability at high temperatures. This is because there is no catalyst forthe diamond to react with and break down.

[0314] After leaching solvent-catalyst metal from the diamond table, itmay be replaced by another metal, metal or metal compound in order toform thermally stable diamond that is stronger than leachedpolycrystalline diamond. If it is intended to weld synthetic diamond ora polycrystalline diamond compact to a substrate or to another surfacesuch as by inertia welding, it may be desirable to use thermally stablediamond due to its resistance to heat generated by the welding process.

[0315] Finishing Methods and Apparatuses

[0316] Once a polycrystalline diamond compact has been sintered, amechanical finishing process may be employed to prepare the finalproduct. The finishing steps explained below are described with respectto finishing a polycrystalline diamond compact, but they could be usedto finish any other surface or any other type of component.

[0317] Prior to the devices herein, the synthetic diamond industry wasfaced with the problem of finishing flat surfaces and thin edges ofdiamond compacts. Methods for removal of large amounts of diamond fromnon-planar surfaces or finishing those surfaces to high degrees ofaccuracy for sphericity, size and surface finish had not been developedin the past.

[0318] Finishing of Superhard Cylindrical and Flat Forms.

[0319] In order to provide a greater perspective on finishing techniquesfor curved and non-planar superhard surfaces for articulatingdiamond-surfaced spinal implants, a description of other finishingtechniques is provided.

[0320] Lapping.

[0321] A wet slurry of diamond grit on cast iron or copper rotatingplates are used to remove material on larger flat surfaces (e.g., up toabout 70 mm. in diameter). End coated cylinders of size ranging fromabout 3 mm to about 70 mm may also be lapped to create flat surfaces.Lapping is generally slow and not dimensionally controllable for depthand layer thickness, although flatness and surface finishes can be heldto very close tolerances.

[0322] Grinding.

[0323] Diamond impregnated grinding wheels are used to shape cylindricaland flat surfaces. Grinding wheels are usually resin bonded in a varietyof different shapes depending on the type of material removal required(i.e., cylindrical centerless grinding or edge grinding).Polycrystalline diamond compacts are difficult to grind, and largepolycrystalline diamond compact surfaces are nearly impossible to grind.Consequently, it is desirable to keep grinding to a minimum, andgrinding is usually confined to a narrow edge or perimeter or to thesharpening of a sized PDC end-coated cylinder or machine tool insert.

[0324] Electro Spark Discharge Grinding (EDG).

[0325] Rough machining of polycrystalline diamond compact may beaccomplished with electro spark discharge grinding (“EDG”) on largediameter (e.g., up to about 70 mm.) flat surfaces. This technologytypically involves the use of a rotating carbon wheel with a positiveelectrical current running against a polycrystalline diamond compactflat surface with a negative electrical potential. The automaticcontrols of the EDG machine maintain proper electrical erosion of thepolycrystalline diamond compact material by controlling variables suchas spark frequency, voltage and others. EDG is typically a moreefficient method for removing larger volumes of diamond than lapping orgrinding. After EDG, the surface must be finish lapped or ground toremove what is referred to as the heat affected area or re-cast layerleft by EDG.

[0326] Wire Electrical Discharge Machining (WEDM).

[0327] WEDM is used to cut superhard parts of various shapes and sizesfrom larger cylinders or flat pieces. Typically, cutting tips andinserts for machine tools and re-shaping cutters for oil well drillingbits represent the greatest use for WEDM in PDC finishing.

[0328] Polishing.

[0329] Polishing superhard surfaces for articulating diamond-surfacedspinal implants to very high tolerances may be accomplished by diamondimpregnated high speed polishing machines. The combination of high speedand high friction temperatures tends to burnish a PDC surface finishedby this method, while maintaining high degrees of flatness, therebyproducing a mirror-like appearance with precise dimensional accuracy.

[0330] b. Finishing A Non-planar Geometry.

[0331] Finishing a non-planar surface (concave non-planar or convexnon-planar) presents a greater problem than finishing a flat surface orthe rounded edge of a cylinder. The total surface area of a sphere to befinished compared to the total surface area of a round end of a cylinderof like radius is four (4) times greater, resulting in the need toremove four (4) times the amount of polycrystalline diamond compactmaterial. The nature of a non-planar surface makes traditionalprocessing techniques such as lapping, grinding and others unusablebecause they are adapted to flat and cylindrical surfaces. The contactpoint on a sphere should be point contact that is tangential to the edgeof the sphere, resulting in a smaller amount of material removed perunit of time, and a proportional increase in finishing time required.Also, the design and types of processing equipment and tooling requiredfor finishing non-planar objects must be more accurate and must functionto closer tolerances than those for other shapes. Non-planar finishingequipment also requires greater degrees of adjustment for positioningthe workpiece and tool ingress and egress.

[0332] The following are steps that may be performed in order to finisha non-planar, rounded or arcuate surface.

[0333] 1.) Rough Machining.

[0334] Initially roughing out the dimensions of the surface using aspecialized electrical discharge machining apparatus may be performed.Referring to FIG. 38, roughing a polycrystalline diamond compact sphere3803 is depicted. A rotator 3802 is provided that is continuouslyrotatable about its longitudinal axis (the z axis depicted). The sphere3803 to be roughed is attached to a spindle of the rotator 3802. Anelectrode 3801 is provided with a contact end 3801A that is shaped toaccommodate the part to be roughed. In this case the contact end 3801Ahas a partially non-planar shape. The electrode 3801 is rotatedcontinuously about its longitudinal axis (the y axis depicted). Angularorientation of the longitudinal axis y of the electrode 3801 withrespect to the longitudinal axis z of the rotator 3802 at a desiredangle β is adjusted to cause the electrode 3801 to remove material fromthe entire non-planar surface of the ball 3803 as desired.

[0335] Thus, the electrode 3801 and the sphere 3803 are rotating aboutdifferent axes. Adjustment of the axes can be used to achieve nearperfect non-planar movement of the part to be roughed. Consequently, anearly perfect non-planar part results from this process. This methodproduces polycrystalline diamond compact non-planar surfaces with a highdegree of sphericity and cut to very close tolerances. By controllingthe amount of current introduced to the erosion process, the depth andamount of the heat affected zone can be minimized. In the case of apolycrystalline diamond compact, the heat affected zone can be kept toabout 3 to 5 microns in depth and is easily removed by grinding andpolishing with diamond impregnated grinding and polishing wheels.

[0336] Referring to FIG. 39, roughing a convex non-planarpolycrystalline diamond compact 1003 such as an articulatingdiamond-surfaced spinal implant is depicted. A rotator 3902 is providedthat is continuously rotatable about its longitudinal axis (the z axisdepicted). The part 3903 to be roughed is attached to a spindle of therotator 3902. An electrode 3901 is provided with a contact end 3901Athat is shaped to accommodate the part to be roughed. The electrode 3901is continuously rotatable about its longitudinal axis (the y axisdepicted). Angular orientation of the longitudinal axis y of theelectrode 3901 with respect to the longitudinal axis z of the rotator3902 at a desired angle β is adjusted to cause the electrode 3901 toremove material from the entire non-planar surface of the articulatingdiamond-surfaced spinal implant 3903 as desired.

[0337] In some embodiments of the devices, multiple electro dischargemachine electrodes will be used in succession in order to machine apart. A battery of electro discharge machines may be employed to carrythis out in assembly line fashion. Further refinements to machiningprocesses and apparatuses are described below.

[0338] Complex positive or negative relief (concave or convex) forms canbe machined into Polycrystalline Diamond Compacts (PDC) orPolycrystalline cubic Boron Nitride (PCBN) parts. This a standardElectrical Discharge Machining (EDM) CNC machining center and suitablymachined electrodes accomplish the desired forms.

[0339]FIG. 40 (side view) and FIG. 40a (end view) show an electrode 4001with a convex form 4002 machined on the active end of the electrode4001, and the electrode base 4005. FIG. 41 (cross section at 41-41) andFIG. 41a show an electrode 4101 with a concave form 4102 and base 4105.The opposite ends of the electrodes are provided with an attachmentmechanism at the base 4105 suitable for the particular EDM machine beingutilized. There are a variety of electrode materials that can beutilized such a copper, copper tungsten, graphite, and combinations ofgraphite and metal mixes. Materials best suited for machining PDC andPCBN are copper tungsten for roughing and pure graphite, or graphitecopper tungsten mixes. Not all EDM machines are capable of machining PDCand PCBN. Only those equipped with capacitor discharge power suppliescan generate spark intensities with enough power to efficiently erodethese materials.

[0340] The actual size of the machined relief form is usually machinedundersized to allow for a suitable spark gap for the burning/erosionprocess to take place. Each spark gap length dictates a set of machiningparameters that must be set by the machine operator to ensure efficientelectrical discharge erosion of the material to be removed. Normally,two to four electrodes are prepared with different spark gap allowances.For example, an electrode using a 0.006 In. spark gap could be preparedfor “roughing,” and an “interim” electrode at 0.002 In. spark gap, and“finishing” electrode at 0.0005 In. spark gap. In each case themachining voltage (V), peak amperage (AP), pulse duration (P), referencefrequency (RF), pulse duration (A), retract duration (R), under-the-cutduration (U), and servo voltage (SV) must be set up within the machinescontrol system.

[0341]FIG. 42 shows an EDM relief form 4201 sinking operation in a PDCinsert part 4202. Table 39 describes the settings for the using a coppertungsten electrode 4203 for roughing and a graphite/copper tungstenelectrode for finishing. The spark gap 4204 is also depicted. TABLE 39Spark Electrode Gap 4203 4204 V AP P RF A R U SV Roughing .006 −2 7 1356 9 0 9 50 Finishing .001 −5 4 2 60 2 0 9 55

[0342] Those familiar with the field of EDM machining will recognizethat variations in the parameters show will be required based on theelectrode configuration, electrode wear rates desired, and surfacefinishes required. Generally, higher machining rates, i.e., highervalues of “V” and “AP” produce higher rates of discharge erosion, butconversely rougher surface finishes.

[0343] Obtaining very smooth and accurate finishes also requires the useof a proper dielectric machining fluid. Synthetic hydrocarbons withsatellite electrodes as disclosed in U.S. Pat. No. 5,773,782, which ishereby incorporated by reference, appear to assist in obtaining highquality surface finishes.

[0344]FIG. 43 shows an embodiment wherein a single ball-nosed (sphericalradiused) EDM electrode 4301 is used to form a concave relief form 4303in a PDC or PCBN part 4302. The electrode 4301 is plunged verticallyinto the part 4302 and then moved laterally to accomplish the rest ofthe desired shape. By programming a CNC system EDM electrode “cuttingpath” of the EDM machine, an infinite variety of concave or convexshapes can be machined. Controlling the rate of “down” plunging and“lateral” cross cutting, and using the correct EDM material will dictatethe quality of the size dimensions and surface finishes obtained.

[0345] 2.) Finish Grinding and Polishing.

[0346] Once the non-planar surface (whether concave or convex) has beenrough machined as described above or by other methods, finish grindingand polishing of a part can take place. Grinding is intended to removethe heat affected zone in the polycrystalline diamond compact materialleft behind by electrodes.

[0347] In some embodiments of the devices, grinding utilizes a grit sizeranging from 100 to 150 according to standard ANSI B74.16-1971 andpolishing utilizes a grit size ranging from 240 to 1500, although gritsize may be selected according to the user's preference. Wheel speed forgrinding should be adjusted by the user to achieve a favorable materialremoval rate, depending on grit size and the material being ground. Asmall amount of experimentation can be used to determine appropriatewheel speed for grinding. Once the spherical surface (whether concave orconvex) has been rough machined as described above or by other methods,finish grinding and polishing of a part can take place. Grinding isintended to remove the heat affected zone in the polycrystalline diamondcompact material left behind by electrodes. Use of the same rotationalgeometry as depicted in FIGS. 9 and 10 allows sphericity of the part tobe maintained while improving its surface finish characteristics.

[0348] Referring to FIG. 44, it can be seen that a rotator 4401 holds apart to be finished 4403, in this case a convex sphere, by use of aspindle. The rotator 4401 is rotated continuously about its longitudinalaxis (the z axis). A grinding or polishing wheel 4402 is provided isrotated continuously about its longitudinal axis (the x axis). Themoving part 4403 is contacted with the moving grinding or polishingwheel 4402. The angular orientation β of the rotator 4401 with respectto the grinding or polishing wheel 4402 may be adjusted and oscillatedto effect grinding or polishing of the part (ball or socket) across itsentire surface and to maintain sphericity.

[0349] Referring to FIG. 45, it can be seen that a rotator 4501 holds apart to be finished 4503, in this case a convex spherical cup or race,by use of a spindle. The rotator 4501 is rotated continuously about itslongitudinal axis (the z axis). A grinding or polishing wheel 4502 isprovided that is continuously rotatable about its longitudinal axis (thex axis). The moving part 4503 is contacted with the moving grinding orpolishing wheel 4502. The angular orientation β of the rotator 4501 withrespect to the grinding or polishing wheel 4502 may be adjusted andoscillated if required to effect grinding or polishing of the partacross the spherical portion of it surface.

[0350] In one embodiment, grinding utilizes a grit size ranging from 100to 150 according to standard ANSI B74.16-1971 and polishing utilizes agrit size ranging from 240 to 1500, although grit size may be selectedaccording to the user's preference. Wheel speed for grinding should beadjusted by the user to achieve a favorable material removal rate,depending on grit size and the material being ground. A small amount ofexperimentation can be used to determine appropriate wheel speed forgrinding.

[0351] As desired, a diamond abrasive hollow grill may be used forpolishing diamond or superhard bearing surfaces. A diamond abrasivehollow grill includes a hollow tube with a diamond matrix of metal,ceramic and resin (polymer) is found.

[0352] If a diamond surface is being polished, then the wheel speed forpolishing mayl be adjusted to cause a temperature increase or heatbuildup on the diamond surface. This heat buildup will cause burnishingof the diamond crystals to create a very smooth and mirror-like lowfriction surface. Actual material removal during polishing of diamond isnot as important as removal sub-micron sized asperities in the surfaceby a high temperature burnishing action of diamond particles rubbingagainst each other. A surface speed of 6000 feet per minute minimum isgenerally required together with a high degree of pressure to carry outburnishing. Surface speeds of 4000 to 10,000 feet per minute arebelieved to be the most desirable range. Depending on pressure appliedto the diamond being polished, polishing may be carried out at fromabout 500 linear feet per minute and 20,000 linear feet per minute.

[0353] Pressure must be applied to the workpiece in order to raise thetemperature of the part being polished and thus to achieve the mostdesired mirror-like polish, but temperature should not be increased tothe point that it causes complete degradation of the resin bond thatholds the diamond polishing wheel matrix together, or resin will bedeposited on the diamond. Excessive heat will also unnecessarily degradethe surface of the diamond.

[0354] Maintaining a constant flow of coolant (such as water) across thediamond surface being polished, maintaining an appropriate wheel speedsuch as 6000 linear feet per minute, applying sufficient pressureagainst the diamond to cause heat buildup but not so much as to degradethe wheel or damage the diamond, and timing the polishing appropriatelyare all important and must all be determined and adjusted according tothe particular equipment being used and the particular part beingpolished. Generally the surface temperature of the diamond beingpolished should not be permitted to rise above 800 degrees Celsius orexcessive degradation of the diamond will occur. Desirable surfacefinishing of the diamond, called burnishing, generally occurs between650 and 750 degrees Celsius.

[0355] During polishing it is important to achieve a surface finish thathas the lowest possible coefficient of friction, thereby providing a lowfriction and long-lasting articulation surface. Preferably, once adiamond or other superhard surface is formed in a bearing component, thesurface is then polished to an Ra value of 0.3 to 0.005 microns.Acceptable polishing will include an Ra value in the range of 0.5 to0.005 microns or less. The parts of the bearing component may bepolished individually before assembly or as a unit after assembly. Othermethods of polishing polycrystalline diamond compacts and othersuperhard materials could be adapted to work with the articulationsurfaces of the invented bearing components, with the objective being toachieve a smooth surface, preferably with an Ra value of 0.01-0.005microns. Further grinding and polishing details are provided below.

[0356]FIG. 46 shows a diamond grinding form 4601 mounted to an arbor4602, which is in turn mounted into the high-speed spindle 4603 of a CNCgrinding machine. The cutting path motion 4604 of the grinding form 4601is controlled by the CNC program allowing the necessary surface coveragerequiring grinding or polishing. The spindle speed is generally relatedto the diameter of the grinding form and the surface speed desired atthe interface with the material 4505 to be removed. The surface speedshould range between 4,000 and 17,000 feet per minuet for both grindingand polishing. For grinding, the basic grinding media for the grindingform should be as “free” cutting as practical with diamond grit sizes inthe range of 80 to 120 microns and concentrations ranging from 75 to125. For polishing the grinding media should not be as “free cutting,”i.e., the grinding form should generally be harder and denser with gritsizes ranging from 120 to 300 microns and concentrations ranging from100 to 150.

[0357] Superhard materials can be more readily removed by grinding ifthe actual area of the material being removed is kept as small aspossible. Ideally the bruiting form 4601 should be rotated to createconditions in the range from 20,000 to 40,000 surface feet per minuetbetween the part 4605 and the bruiting form 4601. Spindle pressurebetween the part 4605 and the bruiting form 4601 operating in a range of10 to 100 Lbs-force producing an interface temperature between 650 and750 Deg C. is required. Cooling water is needed to take away excess heatto keep the part from failing possible. The simplest way to keep thegrind area small is to utilize a small cylindrical contact point(usually a ball form, although a radiused end of a cylinder accomplishesthe same purpose), operating against a larger surface area.

[0358]FIG. 47 shows the tangential area of contact 4620 between thegrinding form 4601 and the substantially larger superhard material 4621.By controlling the path of the grinding form cutter, small grooves 4630(FIG. 48) can be ground into the surface of the superhard material 4621removing the material and leaving small “cusp” 4640 between the adjacentgrooves. As the grooves are cut shallower and closer together the “cusp”4640 become imperceptible to the naked eye and are easily removed bysubsequent polishing operations. The cutter line path of the grindingform cutter should be controlled by programming the CNC system of thegrinding machine to optimize the cusp size, grinding form cutter wear,and material removal rates.

[0359] Bruting

[0360] Obtaining highly polished surface finishes on PolycrystallineDiamond Compact (PDC), Polycrystalline Cubic Boron Nitride (PBCN), andother superhard materials in the range of 0.05 to 0.005 μm can beobtained by running PDC form against the surface to be polished.“Bruiting” or rubbing a diamond surface under high pressure andtemperature against another superhard material degredates or burns awayany positive asperities remaining from previous grinding and polishingoperations producing a surface finish not obtainable in any other way.

[0361]FIG. 49 shows a PDC dome part 4901 on a holder 4904 and being“Bruit Polished” using a PDC bruiting form 4902 being rotated in ahigh-speed spindle 4903. Ideally the bruiting form should be rotated ina range from 20,000 to 40,000 surface feet per minute with the spindlepressure operating in a range of 10 to 100 Lbs-force producing aninterface temperature between 650 and 750 Deg C. Cooling water isgenerally required to take away excess heat to keep the part fromfailing.

[0362]FIG. 50 shows another embodiment of the bruiting polishingtechnique wherein the PDC Bruiting form 5001 is controlled through acomplex surface path 5002 by a CNC system of a grinding machine or a CNCMill equipped with a high-speed spindle to control the point of contact5003 of the form 5001 with a superhard component 5004.

[0363] Use of Cobalt Chrome Molybdenum (CoCrMo) Alloys to AugmentBiocompatability in Polycrystalline Diamond Compacts

[0364] Cobalt and Nickel may be used as catalyst metals for sinteringdiamond powder to produce sintered polycrystalline diamond compacts. Thetoxicity of both Co and Ni is well documented; however, use of CoCralloys which contain Co and Ni have outstanding corrosion resistance andavoid passing on the toxic effects of Co or Ni alone. Use of CoCrMoalloy as a solvent-catalyst metal in the making of sinteredpolycrystalline diamond compacts yields a biocompatible and corrosionresistant material. Such alloys may be defined as any suitablebiocompatible combination of the following metals: Co, Cr, Ni, Mo, Tiand W. Examples include ASTM F-75, F-799 and F-90. Each of these willserve as a solvent-catalyst metal when sintering diamond. Elementalanalysis of the interstitial metal in PDC made with these alloys hasshown that the composition is substantially more corrosion resistantthan PDC made with Co or Ni alone.

[0365] Example Articulating Diamond-Surfaced Spinal Implants

[0366] As used herein, the term “articulating” means that the spinalimplant permits some range of motion, in contrast with fusion therapy inwhich two vertebrae are permanently locked together with respect to eachother. The spinal implants may provide rotation about the axial, coronaland/or sagittal axes and/or translation in the axial plane. The rotationmay permit anterior and posterior bending, lateral bending, and twistingof the torso. The translation may include anterior, posterior andlateral translation. A combination of such rotation and translation isdesired in order to approximate the flexion and extension of a humanspine.

[0367] Also, as used herein “diamond-surfaced” means that the spinalimplant includes diamond on at least a portion of one load bearing orarticulation surface. The implant may include diamond located on asubstrate, it may be solid free-standing diamond, or it may be ofanother structure. The diamond may be sintered polycrystalline diamondthat is a free-standing table or a diamond table sintered or otherwiseattached to a substrate.

[0368] Spinal Disk Implants with Bearing Surfaces Wear Enhanced byDiamond

[0369] The mode of devices included herein includes the enhancement ofspinal disk implants 5100 with bearing surfaces wear-enhanced by theapplication or presence of Poly Crystalline Diamond Compact (PDC). Allof the spinal disk implants FIG. 51 and FIG. 52 including the CervicalDisk (one through seven) 51, the Thoracic Disk (one through twelve) 52,and the Lumbar Disk (one through five) 53 can be enhanced by theapplication of PDC and are included as parts of this devices.

[0370] FIGS. 53, 53-1, 53-2, 53-3 and 53-4 show a spinal diskreplacement implant 101 which uses an Ultra High Molecular WeightPolyethylene (UHMWPE) hemispherical dome 5304 running against a cobaltchrome metal concave cup 5305. The UHMWPE dome insert 5304 is held inplace by a tongue and groove retainer groove 5306.

[0371] FIGS. 54-56 show the disk replacement implant 5101 in a typicalinstallation between two adjacent vertebras 5607, 5608, and FIG'S. 55and 56 depict the relative position of the implant 5101 viewed from theaxial plane view, and the coronal plane view. FIG. 57 shows the relativeside-to-side lateral angular motion possible by using a two partcongruent bearing insert 5101. The angle α typically allows a lateralbending range of plus or minus 10 degrees and is centered about the baseof the spinous process. FIG. 58 shows the rotation β5810 available inthe axial plane which is not limited by the implant 5101 itself, butrather by the surrounding tissue such as muscle and ligaments. FIG. 59shows the flexion angle θ 5911 which is typically 10 to 13 degrees, andthe extension angle φ 5912 of FIG. 60 typically ranging from 5 to 8degrees. A prosthetic spinal disk may permit some or all of theforegoing articulation, in greater or lesser degrees of flexibility.

[0372]FIGS. 61 and 61-1 depict spinal disk implant 600102 including theuse of a metal substrate 60013 on which PDC 60014 has been applied. TheSubstrate/PDC assembly 600103 is held in place by a tongue and grooveretainer groove 60015 in the inferior endplate 60016. The mating convexcup 60017 has PDC 60018 applied directly to the superior endplate 60019.

[0373] The spinal disk implant 600104 shown in FIGS. 62-1 and 62 shows asolid PDC dome insert 60020 held in place in the inferior endplate 60021by a tongue and groove retainer groove 60022. The mating convex cup60023 has PDC 60024 applied directly to the superior endplate 60025.

[0374] The PDC dome insert 600105 shown in FIGS. 63 and 63-1 is held inplace by a surrounding injection molded insert base 60026. The moldedpolymer 60026 surrounds the protrusions 60027 formed in the PDC 60028restricting movement and holding it in place. The injected molded/PDCinsert assembly 600106 is held in place in the inferior endplate 60029by a tongue and groove retainer groove 60030. The mating convex cup60031 has PDC 60032 applied directly to the superior endplate 60033.

[0375] Spinal disk implant 600107 depicted in FIGS. 64 and 64-1 shows asolid PDC dome insert 60033 installed and held in place by aninterference fit between the outside diameter 60034 of the dome insertand the receiving bore 60035 in the inferior endplate 60036. The matingconvex solid PDC cup insert 60037 is also installed and held in place byan interference fit between the outside diameter of the cup insert 60038and the receiving bore 60039 in the superior endplate 60040. Alternateretaining methods to hold the PDC inserts 60033 and 60037 in theinferior 60036 and superior 60040 endplates could involve the use ofbrazing, polymer bonding adhesives, retaining screws, or other standardattachment methods.

[0376] FIG'S. 65 through 65-4 show a three part spinal disk implant600108 with three components including the inferior endplate 60041,superior endplate 60042, both of which contain a convex cup receiver60043, 60044 for the domes 60045 and 60046, of the double hemisphericaldome center part 60047. The two endplates 60041 and 60042 are generallyfabricated form Cobalt Chrome metal but could be fabricated from anyother biocompatible metal with sufficient wear qualities. The centerdouble dome part 60047 is fabricated from High Molecular WeightPolyethylene (UHMWPE).

[0377]FIG. 66 shows a disk replacement implant 600108 in a typicalinstallation between two adjacent vertebras 60048, 60049, and FIG'S. 67and 68 depict the relative position of the implant 600108 viewed fromthe axial plane view, and the coronal plane view.

[0378]FIG. 69 shows the relative side-to-side lateral angular motionpossible by using a three part congruent bearing insert 600108. Theangles α 60050 typically allow a lateral bending range of plus or minus10 degrees. FIG. 70 shows the rotation β 60051 available in the axialplane which is not limited by the implant 600108 itself, but rather bythe surrounding tissue. FIG'S. 71 and 72 shows the flexion angles θ60052 which are typically 10 to 13 degrees, and the extension angle φ60053 FIG. 72 typically ranging from 5 to 8 degrees.

[0379]FIGS. 73 and 73-1 show a typical three piece spinal implant 600109with PDC 60054 and 60055 applied to the inferior endplate 60056 andsuperior endplate 60057 to form the convex cup receivers 60059, 60060.The double hemispherical dome center part 60061 has PDC 60062 applied toform the mating domes 60063, 600 64 for the cup receivers 60059, 60060.

[0380] The three piece spinal implant 600110 shown in FIGS. 74 and 74-1has been enhanced by applying PDC to the inferior 60065 and superior60066 endplate convex cup receivers 60067, 60068. The PDC dome inserts60069, 60070 have been preformed and finished and then injection moldedinto the double dome hemispherical center part 60071. The PDC domesinserts 60069, 60070 are retained in place on the center part by theoverlap 60072 of the injection molded polymer material.

[0381] Solid PDC inferior 60073 and superior 60074 end plates are usedin the three piece spinal implant FIGS. 75 and 75-1 600111 and for thedouble dome center part 60075. The center PDC double dome part 60075 hasbeen injection molded into polymer material to form the completearticulating center part 60076. The overlap 60077 of the injectionmolded polymer material retains the outer ring bumper 60078 onto thesolid or free standing PDC center part 60075.

[0382] The spinal implant 600112 of FIGS. 76, 77 and 77-2 depicts thePDC enhancement of the bearing couple Dome 60079 and the convexcup/trough 60080. The PDC dome insert 60079 is installed into thesuperior endplate 60081 and held in place by an interference fit betweenthe outside diameter 60082 of the dome insert 60079 and the receivingbore 60083 in the superior endplate 60081. The PDC cup/trough insert60080 is installed into the inferior endplate 60084 and held in place byan interference fit between the outside diameter 85 of the cup/troughinsert 60080 and the receiving bore 60086 in the inferior endplate60084. Alternate retaining methods to hold the PDC inserts 60079 and60080 in the inferior 60084 and superior 60081 endplates could involvethe use of brazing, polymer bonding adhesives, retaining screws, orother standard attachment methods. The configuration of the cup/troughinsert 60080 allows for not only angular side-to-side motion and flexionand extension motion, but also provides for translational motion X 60086FIG. 77 in the posterior and anterior directions plus or minus 1 mm ormore if desired. The radial sides of the dome 60079 will not be closeenough to the sides of the cup/trough 60080 FIG. 77-1 to providehydrodynamic support where even minimal bearing clearance has beenprovided, and likewise, the trough ends 60087 will not provide anysupport. Therefore, unlike the fully congruent bearings of the spinalinserts 600200 through 600111, the dome 60079 will be “point loaded” inthe cup/trough 60080 generally promoting extreme bearing loadingconditions. The extreme conditions wrought by non-congruent bearingconfigurations will generally not wear or function well with knownbiocompatible metals. This type of problem, depicted with the spinalimplant 600112, functions extremely well when enhanced by PDC asdescribed above. Test results showing less that 0.3 mg weight loss for30 million unlubricated cycles at five times the anatomical load aretypical. Metal bearings tested under similar conditions would failwithin a few hundred cycles.

[0383]FIG. 79 depicts the spinal implant 600113 section view wherein thecongruent bearings concave cup 60088 and the matching dome 60089 havereceived surface enhancement of PCD.

[0384] The Spinal implant 114 of FIG. 80A and FIG. 80B depicts the PCDsurface enhancement 60090 of the superior insert 60091, and the PCDsurface enhancement 60092 of the inferior insert 60093.

[0385]FIGS. 81A and 81B of the spinal implant 600115 shows the PCDsurface enhancement 60094 of the superior insert 60095, and the PCDsurface enhancement 60096, 60097, 60098 of the inferior insert 60099.

[0386] The spinal implant 600116 shown in FIG. 82A and FIG. 82B depictthe PCD surface enhancement 600100, 600101, 600102 of the superiorinsert 600103, and the PCD surface enhancement 600104, 600105, 600106 ofthe inferior insert 600107.

[0387] The non-congruent spinal implant 600200 FIG. 83A and FIG. 83Bdepict the diamond enhancement 600108, 600109 of the dome surface 600110and the concave running surface 600111. The sides 600112 of the runningsurface 600111 have also been PDC enhanced to prevent metallic wear bycontact with the dome 600110.

[0388]FIG. 84 depicts a similar bearing configuration 600201 wherein theconvex running surface 600111 PDC 600109 enhancement does not includethe sides 600116 of the convex running surface 600111. These implantbearing designs have maximal angular α 600113 and β 600114, andtransitional motion X 600115, but relies totally on the ability of thebearing interface materials to handle the very significant point loadingof the dome 600110 against the concave running surface 600111. Thisbearing, like the bearings 600112 of FIG. 76, benefits greatly from PDCenhancement.

[0389]FIG. 85 depicts a congruent spinal disk bearing 600202 with fourmating surfaces which have been PDC enhanced. Two dome surfaces 600117,600118 have PDC surfacing applied, and two concave cup mating receivingsurfaces 600119, 600120 also have PDC surfacing applied.

[0390] The spinal implant 203 shown in FIG. 86 has been PDC enhanced onthe inferior and superior convex surfaces 600121, 600122 as shown inFIG. 87 and FIG. 87-1 to improve the wear resistance andbiocompatibility.

[0391]FIG. 88 and FIG. 89 depict a spinal disk implant device 600204that has had the inferior convex surface 600123 and superior surface600124 enhanced by the application of PDC.

[0392]FIG. 90 depicts a congruent spinal disk bearing 600205 with twomating surfaces which have been PDC enhanced. The inner ball surface600125 has PDC surfacing applied, and the outer concave cup matingreceiving surfaces 600126 also have PDC surfacing applied for increasedwear resistance and biocompatibility.

[0393] The congruent bearing spinal implant shown in FIG. 91 as 600206has been PDC enhanced on the inferior dome surface 600127, and thesuperior convex cup surface 600128 to improve the wear resistance andbiocompatibility.

[0394]FIG. 92 depicts a congruent spinal disk bearing 600207 with twomating surfaces which have been PDC enhanced. The inner ball surface600129 has PDC surfacing applied, and the outer concave cup matingreceiving surfaces 600130 also have PDC surfacing applied for increasedwear resistance and biocompatibility.

[0395] Application of Polycrysilline Dimond Compacts For Non-CongruantSpinal Implant Bearing Surfaces

[0396] Duplicating the anatomical motion of the human spine using spinaldisk replacement implants is quite challenging. The motions that must bereplicated in the implant device are originally the result of compoundangular and translational motions allowed through the compliance of thepillow-like spine disk. The human vertebral disk has the ability toreshape itself instantaneously predicated on the vector forces appliedto it while at the same time providing a flexible attachment between twoadjacent vertebras. For example, side-to-side bending motion in thecoronal plane causes the spinal disk pad to become thin on the inside ofthe bend angle and larger on the outside of the bend angle. With theangular wedge type reshaping of the spinal disk in the side-to-sidemotion there is also some lateral translation or parallel sliding of thetwo adjacent vertebras. This same motion condition is also exhibitedwith flexion and extension of the body in the sagittal plane; however,the translational motion is significantly greater, often ranging from 1to 2 mm. Lateral rotation in the axial plane does not occur around thecenter of the spinal disk. The actual center of rotation is posterior tothe spinal cord channel, often by several millimeters. This lattermotion is almost completely translational parallel motion with thecommon centers of the adjacent vertebras swinging in an arc.

[0397] Spinal disc implants utilizing congruent dome and cup bearings600208 as in FIG. 93 simply can not adequately duplicate the compoundmotions exhibited in the normal human anatomical motion. The verycongruency of the bearing surfaces makes any kind of translationalmotion impossible. Lateral rotation FIG. 93-1 in the axial plane angle β600131, and flexion of FIG. 59 angle 0 5911, and FIG. 60 extension angleφ 5912 in the sagittal plane are severely restricted. This conditionprevents the realization of full anatomical restoration followingsurgery and tends to place additional collateral forces on the adjacentspinal disc above and below the spinal disk implant leading to possiblefuture problems.

[0398] The use of disc implants 600209 employing non-congruent dome andcup bearings of FIGS. 93 and 93-1 can provide substantially superior ornear perfect anatomical duplication. By employing a dome, or similardome shape, 600132 operating in a convex oval, kidney, or other suitablyshaped mating receiver 600133 both angular and translational motion canbe fully duplicated.

[0399] However, non-congruent bearings as utilized in spinal implantstend to produce overwhelming “point load forces” for typicalbiocompatible metals where the dome contacts the mating convex bearingreceiver. These “point load forces” quickly wear away the bearingsurfaces generally making them inoperable and producing wear particleswhich react with the surrounding tissue.

[0400] Polycrystalline diamond compact (PDC) utilized in spinal implantswith non-congruent bearing surfaces completely ameliorates the “pointload forces” problem associated with these types of bearings. Oneembodiment of the devices includes the use of PDC for the convex domeand convex articulating surface of a non-congruent spinal implantbearing. FIGS. 94 and 94-1 depict a non-congruent spinal implant bearing600209 wherein the dome 600132 has been fabricated using PDC, and alsothe convex articulating surface 600133 has been fabricated using PDC. Toaccomplish the necessary compound angular and translational motionrequired the shape of the dome 600132 would be generally hemisphericalbut could be elliptical, oval, flattened, or any other configurationthat would allow for the motion required. The convex articulatingsurface 600133 could be shaped to allow the dome 600132 to not only rockangularly in the direction desired but to also translate horizontally inthe axial plane X 600134.

[0401]FIGS. 94a and 94 a-1 depict an alternative sprinal prosthesis600140 a in which a hemispherical protrusion 600140 a 1 rides along atrough 600140 a 1 along an arc of a circle defined by circle center Clocated at the base of the spinal process, and radius R to provide βdegrees of rotational movement within the trough. The trough has akidney bean appearance.

[0402] The actual contour of the convex surface of the recess can bedesigned to meet any special angular and translational requirement.FIGS. 95, 95-1 and 95-2 show a spinal insert 600210 configurationwherein the radius r2 600135 of the convex articulating surface 600138are significantly larger than the dome radius r1 600136 allowing thedome 600137 to rotate freely, but to also translate in any directionuntil restrained from further movement by the surrounding tissue.

[0403] FIGS. 96, 96-1 and 96-2 depict a modified articulating surfaces600211 wherein the convex articulating surface radius r4 600138 issignificantly larger than the end radiuses r3 600139, and the radius r6600140 is significantly larger than the end radiuses r5 600141. Thecenter radiuses r4 600138 and r6 600140 can be equal, but may also beunequal, also the end radiuses r3 600139 and r5 600141 can be equal, butmay also be unequal. The dome radius r2 600142 would generally beslightly smaller than the smallest of radiuses r3 600139 and r5 600141.

[0404] FIGS. 97, 97-1 and 97-2 depict a modified articulating surfaces600212 wherein the recessed articulating surface has a flat area 600143and end radiuses r3 600144. The end radiuses r3 600144 and r4 600145 canbe equal, but may also be unequal. The dome radius r2 600146 wouldgenerally be slightly smaller than the smallest of radiuses r3 600144and r4 600145.

[0405] FIGS. 98, 98-1 and 98-2 depict a modified articulating surfaces600213 wherein the convex articulating surface has a conical area 600147defined by the angle φ 600148 and end radiuses r3 600149. The endradiuses r3 600149 and r4 600150 can be equal, but may also be unequal.The dome radius r2 600151 would generally be slightly smaller than thesmallest of radiuses r3 600149 and r4 600150.

[0406] FIGS. 99-1 and 49-2 depict a modified articulating surface 600214wherein the convex articulating surface is an elliptically shaped area600152. The elliptical shape 600152 can be equal to the elliptical shape600153, but may also be unequal or another shape configuration. The domeradius r2 600154 would generally be of size to allow for the requiredangular and transitional motion.

[0407] FIGS. 100, 100-1 and 100-2 depict a modified articulating surface600215 wherein the convex articulating surface 600155 is a defined by athree dimensional mathematically defined function of the general form:

Surface=f(r _(ijk),θ_(ijk),φ_(ijk))

[0408] The dome radius r2 600156 would generally be of size to allow forthe required angular and transitional motion.

[0409]FIGS. 101 and 101-1 show modified articulating surfaces for athree part spinal implant insert 600216 configuration wherein the radiusr1 600157 of the convex articulating surface 600158 is significantlylarger than the dome radiuses r2 600159 allowing the domes to rotatefreely, but to also translate in any direction until restrained fromfurther movement by the surrounding tissue.

[0410] FIGS. 102, 102-1 and 102-2 depict modified articulating surfacesfor a three part spinal implant 600217 wherein the convex articulatingsurface radiuses r4 600159 is significantly larger than the end radiusesr3 600160 and the radius r6 600161 is significantly larger than the endradiuses r5 600162. The center radiuses r4 600159 and r6 600161 can beequal, but may also be unequal, also the end radiuses r3 600160 and r5600162 can be equal, but may also be unequal. The dome radius r2 600163would generally be slightly smaller than the smallest of radiuses r3600160 and r5 600162.

[0411] FIGS. 103, 103-1 and 103-2 depict articulating surfaces for athree part spinal implant 600218 wherein the recessed articulatingsurface has a flat area 600164 and end radiuses r3 600165. The endradiuses r3 600165 and r4 600166 can be equal, but may also be unequal.The dome radius r2 600167 would generally be slightly smaller than thesmallest of radiuses r3 600165 and r4 600166.

[0412] FIGS. 104, 104-1 and 104-2 depict an articulating surfaces for athree part spinal implant 600219 wherein the convex articulating surfacehas a conical area 600168 defined by the angle φ600 169 and end radiusesr3 600170. The end radiuses r3 600170 and r4 600171 can be equal, butmay also be unequal. The dome radius r2 600172 would generally beslightly smaller than the smallest of radiuses r3 600170 and r4 600171.

[0413] FIGS. 105, 105-1 and 105-2 depict an articulating surface for athree part spinal implant 600220 wherein the convex articulating surfaceis an elliptically shaped area 600173. The elliptical shape 600173 canbe equal to the elliptical shape 600174, but may also be unequal oranother shape configuration. The dome radius r2 600175 would generallybe of size to allow for the required angular and transitional motion.

[0414] FIGS. 106, 106-1 and 106-2 depict articulating surfaces for athree part spinal implant 600221 wherein the convex articulating surface600 176 is a defined by a three dimensional mathematically definedfunction of the general form:

Surface=f(r _(ijk),θ_(ijk), φ_(ijk))

[0415] The dome radius r2 600177 would generally be of size to allow forthe required angular and transitional motion.

[0416]FIGS. 107 and 107-2 depict a three part spinal implant 600222wherein the inferior endplate 600178 and the superior endplate 600179have been fabricated using PDC. The outer surfaces 600180, 600181 andthe attachment protrusions 600182 which will contact the adjacentvertebrae following surgery have been chemically leached using asuitable acid leaching bath such as nitric-hydro sulfuric acid to removethe interstitial metal between the diamond crystals. The depth of theleached areas 600180, 600181, 600182 would generally range from 0.5 to1.5 mm or more. The voids left between the diamond crystals would beavailable for bone in growth infusion, or the application of other bonegrowth surfaces, or bone growth accelerators such as Hydroxyl Appetite.

[0417]FIGS. 108 and 108-1 depict a two part spinal implant 600223wherein the inferior endplate 600183 and the superior endplate 600184have been fabricated using PDC. The outer surfaces 600185, 600186 andthe attachment protrusions 600187 which will contact the adjacentvertebrae following surgery have been chemically leached using asuitable acid leaching bath such as nitric-hydro sulfuric acid to removethe interstitial metal between the diamond crystals. The depth of theleached areas 600185, 600186, 600187 would generally range from 0.5 to1.5 mm or more. The voids left between the diamond crystals would beavailable for bone in growth infusion, or the application of other bonegrowth surfaces or bone growth accelerators. In addition, any bonemating surface depicted anywhere herein could include a bone growthaccelerator, a roughened or textured surface to promote bone fixation,pores to permit bone ingrowth, and protrusions to achieve mechanicalbone fixation. In addition, adhesives, glues or epoxies may also be usedto achieve bone fixation.

[0418] Spinal Implant Fixation Method Using Screws With PartialHemaspherical Engagement

[0419] The devices shown in FIGS. 109, 109-1, 109-2, 109-3 a, 109-3 b,109-4 and 109-5 disclose a method and apparatus by which one or morescrews 7001 may be used to assist in the installation of a spinalimplant appliance 7002, provide partial fixation during the period ofbone in-growth to the receptor surfaces 7003 of the appliance 7002, andfull fixation for the life of the implant. Another object of thisdevices is to provide fixation without any protrusion of the fixationscrews 7001 or other components into the anterior or posterior areassurrounding the spinal implant device 7002.

[0420] Fixation of the spinal implant device 7002 is accomplished by theengagement of slightly less than one-half of the hemispherical portionof the full length of the screw threads 7004 of the fixation screws 7001into the adjacent vertebral bones 7005 as depicted in the Figures. Thecomplementary pressure of the tissue tending to hold and draw the twocorresponding vertebra 7004 together generally provides contactpressures 7006 normal toward the screw thread 7004 surfaces and the bonesurface 7007 allowing adequate frictional and buttressing fixation. Thescrews 7001 are held captive in the appliance 7002 superior 7008 andinferior 7009 plate surfaces 7003 by machining the screw holes 70010slightly below the plate surfaces 7003 of the appliance 7002 whichinterfaces with the bone surfaces 7007. The centerline locatingdimension β 70011 of the screw holes 70010 can be adjusted based on thediameter 70012 of the screw 7001 to ensure that part of the platematerial 70013 extends slightly beyond the centerline of the screw 7001securing it in place within the plates 7008 and 7009. The screw holes70010 in the superior 7008 and the inferior 7009 plates of the implantdevice 7002 can be a drilled hole only 70014 as shown in FIG. 109-3 awith a diameter slightly larger than the major diameter 70012 of thescrews 7001, or tap drilled to the minor of the screw 7001 and thenthreaded 70015 as shown in FIG. 109-3 b.

[0421] One, two, or more fixation screws 7001 could be used to providethe device 7002 securement. The fixation screws 7001 can also be locatedat an angel α 70016 ranging between 0.0 Deg and 90 Deg. One embodimentwould locate two screws at an angle α 70016 of approximately 35 Deg.which provides the most favorable strain resistance against componentforces exerted laterally along the horizontal plane of the body. Threadsin the vertebrae 7005 bone surface 7007 can be created by using thescrew 7001 only, or by pre-cutting the threads 70015 using a typicalthread tap of the correct size, form, and length in conjunction with asuitable tap drill hole location fixture and tapping fixture.

[0422] The head 70017 of the securing screws 7001 is recessed into arelief counter-bore 70018 of FIG. 109-5 to prevent any protrusion at theanterior face of the spinal implant 7002.

[0423] The surfaces 7003 of the superior 7008 and inferior 7009 platesof the spinal implant device 2 may be prepared for bone in growth by theapplication of Hydroxy Apatite coating, chemical coating, attached metalbeads, etched surfacing, leached poly crystalline diamond, or any othertreatment that would promote bone ingrowth and attachment.

[0424] Spinal Implant Fixation Method Using Screws With Angular VectorBone Engagement

[0425] The devices shown in FIGS. 110, 110-1, 110-2 and 110-3 disclosemethods and apparatuses by which one or more screws 8001 may be used toassist in the installation of a spinal implant appliance 8002, providepartial fixation during the period of bone ingrowth to the receptorsurfaces 8003 of the appliance 8002, and full fixation for the life ofthe implant. Another object of this devices is to provide fixationwithout any protrusion of the fixation screws 8001 or other componentsinto the anterior or posterior areas surrounding the spinal implantdevice 8002.

[0426] Fixation of the spinal implant device 8002 is accomplished by theengagement of the screw threads 8004 of the fixation screws 8001 intothe adjacent vertebral bones 8005 as more fully depicted in the Figures.The complementary pressure of the tissue tending to hold and draw thetwo corresponding vertebra 8005 together generally provides contactpressure 8006 toward the bone surfaces 8007 and is augmented bycomponent forces associated with the holding resistance of the screws8001 acting at angles σ 8008 and angle α 8009.

[0427] One, two, or more fixation screws 8001 could be used to providethe device 8002 securement. The fixation screws 8001 can be located atan angel α 8009 ranging between 0.0 Deg and 90 Deg. and angle σ 8008ranging between approximately 10 Deg. and 45 Deg. One embodiment wouldlocate two screws at an angle σ 8008 of approximately 25 Deg. and angleα 8009 at approximately 35 Deg. which would provide the most favorablestrain resistance against component forces exerted axially along themedian/coronal planes and laterally along the horizontal plane of thebody. Threads in the vertebrae 8005 bone can be created by using thescrew 8001 only, or by pre-cutting the threads 80010 FIG. 110-3 using atypical thread tap of the correct size, form, and length in conjunctionwith a suitable tap drill hole location fixture and tapping fixture.

[0428] The head 80011 of the securing screws 8001 is recessed into arelief counter-bore 80012 of FIG. 110-3 to prevent any protrusion at theanterior face of the spinal implant 8002.

[0429] The surfaces 8003 of the superior 80013 and inferior 80014 platesof the spinal implant device 8002 may be prepared for bone in growth andattachment.

[0430] Spinal Implant Fixation Method Using Screws With Angular VectorPlate Engagement

[0431] The devices shown in FIGS. 111, 111-1, 111-2 and 111-3 disclosesmethods and apparatuses by which one or more screws 8501 may be used toassist in the installation of a spinal implant appliance 8502, providepartial fixation during the period of bone in-growth to the receptorsurfaces 8503 of the appliance 8502, and full fixation for the life ofthe implant. Another object of this devices is to provide fixationwithout any protrusion of the fixation screws 8501 or other componentsinto the anterior or posterior areas surrounding the spinal implantdevice 8502.

[0432] Fixation of the spinal implant device 8502 is accomplished by theengagement of the screw threads 8504 of the fixation screws 8501 intothe superior 8505 and inferior 8506 implant plates 8507 after havingpassed through the adjacent vertebral bones 8508 as more fully depictedin the Figures. The complementary pressure of the tissue tending to holdand draw the two corresponding vertebra 8508 together generally providescontact pressure 8509 toward the bone surfaces 85010 and is augmented bycomponent forces associated with the holding resistance of the screws8501 acting at angles σ 85011 and angle α 85012.

[0433] One, two, or more fixation screws 8501 could be used to providethe device 8502 securement. The fixation screws 8501 can be located atan angel α 85012 ranging between 0.0 Deg and 90 Deg. and angle σ 85011ranging between approximately 10 Deg. and 45 Deg. One embodiment wouldlocate two screws 8501 at an angle σ 85011 of approximately 25 Deg. andangle α 85012 at approximately 35 Deg. which would provide the mostfavorable strain resistance against component forces exerted axiallyalong the median/coronal planes and laterally along the horizontal planeof the body. The fixation screws engage the superior 8505 and inferior8506 plates 8507 at in pre-threaded holes 85013. The fixation screws8501 can be threaded along the full length of the screw 8501, or onlyfor the length which engages the superior 8505 and inferior 8506 plates8507. Clearance holes for the fixation screws 8501 are pre-drilled usinga suitable location fixture to ensure proper location and engagement ofthe screws 8501 into the superior 5850 and inferior 8506 plates 8507.

[0434] The head 85014 of the securing screws 8501 is recessed into arelief counter-bore 85015 to prevent any protrusion at the anterior faceof the spinal implant 8502.

[0435] The surfaces 8503 of the superior 8505 and inferior 8506 plates8507 of the spinal implant device 8502 may be prepared for bone ingrowth.

[0436] Spinal Implant Fixation Method Using Securment Lugs WithAttachment Screws and Anti Rotation Positionioners

[0437] The devices shown in FIGS. 112, 112-1, 112-2 and 112-3 disclosemethod and apparatuses by which one or more lugs or clips 9001 may beused to assist in the installation of a spinal implant appliance 9002,provide partial fixation during the period of bone in-growth to thereceptor surfaces 9003 of the appliance 9002, and full fixation for thelife of the implant. Another object of this device is to providefixation without any protrusion of the fixation clips 9001, screws 9004or other components into the anterior or posterior areas surrounding thespinal implant device 9002.

[0438] Fixation of the spinal implant device 9002 is accomplished by theengagement of the lugs 9001 into the recesses 9005 previously machinedinto the vertebra by the surgeon. The clips 9001 may be stabilized bythe use of a square or rectangular matching tongue protrusions 9006 andgrooves 9007 running parallel and perpendicular to the median plane ofthe body. Other tongue and groove configurations such as the angulartongue 9008 and angular groove, or a hemispherical tongue and groovescould be used to prevent rotation of the clip.

[0439] The head 90012 of the securing screw 9004 is recessed into arelief counter-bore 90013 to prevent any protrusion at the anterior faceof the spinal implant 9002. The clip 9001 is also rounded 90014 andrecessed 90015 to prevent any protrusion at the anterior face of thespinal implant 9002. The surfaces 9003 of the superior 90016 andinferior 90017 plates of the spinal implant device 9002 may be preparedfor bone in growth.

[0440] While the present devices and methods have been described andillustrated in conjunction with a number of specific configurations,those skilled in the art will appreciate that variations andmodifications may be made without departing from the principles hereinillustrated, described, and claimed. The present invention, as definedby the appended claims, may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. Theconfigurations described herein are to be considered in all respects asonly illustrative, and not restrictive. All changes which come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

1. An articulating diamond-surfaced prosthetic spinal implant forimplantation between vertebrae in a human body, the implant comprising:a first component, said first component having a convex protruding domemember, said dome member including a first component load bearing andarticulation surface, said first component load bearing and articulationsurface being formed at least in part by a sintered polycrystallinediamond table, said sintered polycrystalline diamond table in said firstcomponent serving to provide a durable, biocompatible and low-frictionsurface for articulation of the implant, a second component, said secondcomponent having a concave trough, said trough having a shape and sizethat permits said protruding dome member to protrude therein, saidtrough having a shape and size that permits contact of said protrudingdome member therewith at a plurality of contact points, said troughincluding a second component load bearing and articulation surface, saidsecond component load bearing and articulation surface being formed atleast in part by a sintered polycrystalline diamond table, said sinteredpolycrystalline diamond table in said second component serving toprovide a durable, biocompatible and low-friction surface forarticulation of the implant, said first component being movable withrespect to said second component in at a point that has diamond todiamond contact between said first and second components.
 2. An implantas recited in claim 1 wherein said first component and said secondcomponent are able to articulate with respect to each other to providerotation about the axial, coronal and/or sagittal axes of the humanspine.
 3. An implant as recited in claim 1 wherein said first componentand said second component are able to articulate with respect to eachother to provide translation in the axial plane of a human spine.
 4. Animplant as recited in claim 1 wherein said first component and saidsecond component are able to articulate with respect to each other toprovide rotation about the axial, coronal and/or sagittal axes of thehuman spine; and wherein said first component and said second componentare able to articulate with respect to each other to provide translationin the axial plane of a human spine; and wherein said rotation andtranslation accommodate anterior bending, posterior bending, lateralbending, twisting of a spine about its longitudinal axis, anteriortranslation, posterior translation and lateral translation.
 5. Animplant as recited in claim 1 wherein said dome member has a shape thatis at least partially spherical convex.
 6. An implant as recited inclaim 1 wherein said first and second components include congruentbearing surfaces.
 7. An implant as recited in claim 1 wherein said firstand second components include non-congruent bearing surfaces.
 8. Animplant as recited in claim 1 further comprising: carbon to carbon bondsin at least one of said sintered polycrystalline diamond table.
 9. Animplant as recited in claim 8 further comprising: sp3 carbon bonds in atleast one of said sintered polycrystalline diamond table.
 10. An implantas recited in claim 9 further comprising: a crystalline diamondstructure in at least one of said sintered polycrystalline diamondtable.
 11. An implant as recited in claim 10 further comprising:interstitial spaces in said crystalline diamond structure.
 12. Animplant as recited in claim 11 further comprising: solvent-catalystmetal in said interstitial spaces.
 13. An implant as recited in claim 12further comprising: diamond to metal bonds between said solvent-catalystmetal and diamond in said sintered polycrystalline diamond table.
 14. Animplant as recited in claim 13 wherein said solvent-catalyst metal wasused to facilitate sintering of said polycrystalline diamond compact athigh temperature and high pressure.
 15. An implant as recited in claim12 wherein said solvent-catalyst metal includes a material selected fromthe group consisting of Co, Cr and Mo.
 16. An implant recited in claim12 wherein said solvent-catalyst metal includes CoCr.
 17. An implant asrecited in claim 12 wherein said solvent-catalyst metal includes CoCrMo.18. An implant as recited in claim 1 further comprising a gradienttransition zone in at least one of said sintered polycrystalline diamondtables, said gradient transition zone having a first side and a second,said gradient transition zone having both solvent-catalyst metal anddiamond therein, and said gradient transition zone exhibiting atransition of ratios of percentage content of solvent-catalyst metal todiamond from said first side to said second side such that at a firstpoint in said gradient transition zone, the ratio of percentage contentof solvent-catalyst metal to diamond is greater than it is at a secondpoint in gradient transition zone.
 19. An implant as recited in claim 1wherein at least one of said sintered polycrystalline diamond tables isa free standing diamond table.
 20. An implant as recited in claim 1wherein at least one of said sintered polycrystalline diamond tablesincludes diamond sintered to a substrate.
 21. An implant as recited inclaim 1 wherein at least one of said sintered polycrystalline diamondtables includes a diamond table attached to a substrate.
 22. Anarticulating diamond-surfaced prosthetic spinal implant for implantationbetween vertebrae in a human body, the implant comprising: a protrusion,a protrusion load bearing and articulation surface located on saidprotrusion, said protrusion load bearing and articulation surface beingformed at least in part by diamond, a receptacle, a receptacle loadbearing and articulation surface located on said receptacle, saidreceptacle load bearing and articulation surface being formed at leastin part by diamond, said protrusion and said receptacle being sized andshaped to accommodate said protrusion protruding into said receptacle,and contact of said protrusion load bearing and articulation surfacewith said receptacle load bearing and articulation surface, said contactof said protrusion with said receptacle being accomplished by diamond todiamond contact of said protrusion and receptacle load bearing andarticulation surfaces.
 23. An articulating diamond-surfaced prostheticspinal implant for implantation between vertebrae in a human body, theimplant comprising: a protrusion, a protrusion load bearing andarticulation surface located on said protrusion, said protrusion loadbearing and articulation surface being formed at least in part bydiamond, a receptacle, a receptacle load bearing and articulationsurface located on said receptacle, said receptacle load bearing andarticulation surface being formed at least in part by diamond, saidprotrusion and said receptacle being sized and shaped to accommodatesaid protrusion protruding into said receptacle, and said protrusionload bearing and articulation surface contacting said receptacle loadbearing and articulation surface, said contact of said protrusion withsaid receptacle being accomplished by diamond to diamond contact of saidprotrusion and receptacle load bearing and articulation surfaces, saidcontact of said protrusion with said receptacle occurring at a diamondto diamond contact point where diamond of said protrusion contactsdiamond of said receptacle, said protrusion being pivotally movable withrespect to said receptacle about said diamond to diamond contact pointto provide translational or rotational movement of said protrusion withrespect to said receptacle.
 24. An articulating diamond-surfacedprosthetic spinal implant for implantation between vertebrae in a humanbody, the implant comprising: a protrusion, a protrusion load bearingand articulation surface located on said protrusion, said protrusionload bearing and articulation surface being formed at least in part bydiamond, said protrusion having a curvature defined by at least oneradius R1, a receptacle, a receptacle load bearing and articulationsurface located on said receptacle, said receptacle load bearing andarticulation surface being formed at least in part by diamond, saidreceptacle having a curvature defined by at least one radius R2, saidprotrusion and said receptacle being sized and curved to accommodatesaid protrusion protruding into said receptacle, and to accommodate saidprotrusion load bearing and articulation surface contacting saidreceptacle load bearing and articulation surface, said contact of saidprotrusion with said receptacle being accomplished by diamond to diamondcontact of said protrusion and receptacle load bearing and articulationsurfaces, said contact of said protrusion with said receptacle occurringat a diamond to diamond contact point where diamond of said protrusioncontacts diamond of said receptacle, said protrusion beingtranslationally movable with respect to said receptacle in the axialplan of a human spine, said translational movement being accomplished bya sliding or rolling movement of diamond against diamond; wherein R1 andR2 are chosen to accommodate said translational movement; and wherein atleast some of said translational movement occurs in the axial plane of ahuman spine about an arc of a circle having a radius R3 whose center islocated at the base of the spinal process of a human spine, and whereinR3 is not equal to R1 or R2.